5000 electrical switchyard design report group 8 final

8/13/2019 5000 Electrical Switchyard Design Report Group 8 Final

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Nuclear Plant Design

Design Description for Switchyard

Terry Price 100350844Brian Liang 100442577Thayer Bai 100425385

Alex Robitaille 100423915Nadeem Murji 100394550Karndeep Gill 100367967


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Switchyard Conceptual Design Document for the ART25 Nuclear Power Plant

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Contents

Acronyms ........................................................................................................................................ 3

Executive Summary ......................................................................................................................... 3

Design Overview ............................................................................................................................. 4System Overview ............................................................................................................................ 6

Site Layout ....................................................................................................................................... 8

System Components ..................................................................................................................... 10

Distribution Bus......................................................................................................................... 10

Wave Trap ................................................................................................................................. 11

Insulator .................................................................................................................................... 11

Lightning Arrestor ..................................................................................................................... 12

Resistor Bank ............................................................................................................................. 12

Step-Up Transformer ................................................................................................................ 13

Step-Down Transformer ........................................................................................................... 15

Emergency Circuit Breakers ...................................................................................................... 16

Emergency Circuit Connectors .................................................................................................. 16

Connectivity Switching Mechanism .......................................................................................... 17

Galvanometers .......................................................................................................................... 18

Voltage Stabilizing Autotransformer ........................................................................................ 19

Grounding ................................................................................................................................. 20

Soil Preparation ..................................................................................................................... 21

Ground Rod Design ............................................................................................................... 21

Filter Capacitor Banks ............................................................................................................... 21

Phase Angle Adjusters............................................................................................................... 22

Emergency Backup Power Redirection Bus .............................................................................. 24

Output Monitoring .................................................................................................................... 24

Digital Control Computer .......................................................................................................... 24

Site Features ............................................................................................................................. 25

Fencing .................................................................................................................................. 26

Fire Protection .......................................................................................................................... 26

Site Grading ............................................................................................................................... 26

Environmental Impact............................................................................................................... 27


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Review of Design Requirements ................................................................................................... 27

Functional Requirements .......................................................................................................... 28

Performance Requirements ...................................................................................................... 28

Safety Requirements ................................................................................................................. 29

Client Requirements: ................................................................................................................ 32

Reliability and Maintainability Requirements .......................................................................... 32

Cost Requirements .................................................................................................................... 33

Environmental Requirements ................................................................................................... 33

Human Factor Requirements .................................................................................................... 34

Layout Requirements ................................................................................................................ 34

Assumptions .................................................................................................................................. 35

Turbine Generator Assumptions............................................................................................... 35

Bibliography .................................................................................................................................. 35

Acronyms

CSM Connectivity Switching Mechanism

ECBD Emergency Circuit Breaker Device

ECCD Emergency Circuit Connector Device

Executive Summary

The report that follows details the conceptual design of the electrical switchyard for the

ART25 nuclear power-plant. This switchyard transfers power from the electrical power

generators, conditions it, and supplies it to both the electrical power grid and the nuclear

power-plant itself. Furthermore, the switchyard provides backup power routing capabilities

and some electrical power dissipation capability. Components designed include: the

distribution bus, the wave trap, the insulators, the lighting arrestors, the resistor banks, the

step-up and step-down transformers, the emergency circuit connectors, the emergency circuit

breakers, the galvanometers, the voltage stabilizing autotransformers, grounding, site layout,

filter capacitor banks, phase angle adjusters, the emergency backup power distribution bus, the


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supplied from the generator to the plant. This connectivity and re-routing is controlled by a

CSM.

Additionally, the entire switchyard can be isolated from the grid and the plant via a CSM.

Connectivity to the plant and grid is maintained with independent parallel connections so that

any maintenance operations can occur without discontinuing power distribution.

Grounding shall be provided via a pair of conductive rods driven into the ground. Using

two conductive rods provides redundancy in case of any sort of system failure. All systems will

be provided with a ground. Furthermore, to mitigate against the risk of spatial transients, the

grounding rods shall be embedded at spatially distinct locations.

Power monitoring is a key capability of the switchyard. All power paths into the switchyard, out

of the switchyard, and between elements within the switchyard must have their parameters

continuously monitored so that any transients can be monitored and interrupted to prevent

system damage. The particular parameters to be monitored shall be noted in the system

components section of the report.

The parameters of the supplied power shall be controlled to match grid and plant-system

requirements through a system of autotransformers, to adjust voltage output, and capacitor

banks, to adjust phase angle.

The entire switchyard shall be controlled via a control room. This control room is to

provide a suitable working environment for switchyard personnel and includes amenities that

include a break-room, wash-rooms, heating, air conditioning. From within this control room,system performance can be monitored and the parameters of various elements of the

switchyard can be altered. Furthermore, a data connection is installed between the switchyard

control room and the reactor control room so that information about the grid demand and

switchyard status can be communicated to the reactor control room.


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System Overview

A functional diagram of the system is as follows:

Electric Generator

Step-Up

TransformerAutotransformer

Filter Capacitors

Banks

To Power Grid

Distribution Bus

Step-Down

TransformerAutotransformer

Filter Capacitors

Banks

Phase Angle

Adjustment

Phase Angle

Adjustment

Single Phase Tap-Off

Three-Phase PowerPhase Angle

Adjustment

To Plant Single

Phase Power

To Plant Three

Phase Power

Resistor Banks

Wavetrap

From BackupEmergency Power

Distribution System

Figure 1 System Layout

The switchyard is divided into three sub-systems: distribution bus and power dissipation

area; the grid-side power distribution system; and, the plant-side power distribution system.

The electric generator provides power to the distribution bus. The distribution bus distributes

power in three directions: upwards to the plant, right to the resistor banks, and down to the

power grid. The resistor banks dissipate any excess-power transients, in particular the Back-

EMF from the transformers or electric generator.

Considering the power-grid side of the switchyard, the step-up transformer is steps up

the voltage from that which is provided by the generator to that which is accepted by the grid.

The autotransformer (variac) is a transformer is capable of differentially changing its winding

ratio so that the voltage output of the step-up transformer matches the voltage demanded by

the power-grid. The filter capacitor banks filter out any short time-scale power transients that


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might occur in system. The phase angle adjustment is achieved by a bank of variable capacitors

that align the output phase angle to the phase angle of the grid.

The plant-side power side of the switch yard works in a manner similar to that of the

power-grid side of the switch yard, except for several differences. First, there are two outputs:

three-phase power and single-phase power. The three-phase power system directly feeds the

three-phase power coming off the electric generator through the step-down transformer and

into phase angle adjustment whereupon it is directly fed into the plants three-phase power

system. The single-phase power system takes a single phase out of the three-phase power,

feeding it to phase-angle adjustment and then to the plants single phase power output.

Between each element in the system, a current sensing galvanometer is installed. This

galvanometer trips an over-current protection system if it detects a high-current transient. This

overcurrent protection system signals the emergency circuit breakers that connect the

switchyard to the electric generator to trip, thereby disconnecting the switchyard from the

power source. The element that is experiencing the over-current transient is also disconnected

from the rest of the system using emergency circuit breakers that are installed between each

element of the system. The element that is experiencing the over-current transient is thensunk to the resistor banks through an emergency circuit connector so that any stored charge in

the element can be dissipated safely.

Continuous inspection of the switchyard shall be performed. This inspection looks for changes

in operating parameter, physical attributes and human performance of the switchyard and

adjusts them if the drift too far off their nominal values.

Conductors transmitting power to each component in the switchyard shall be insulated with a

thickness of insulation that prevents electrical arcing to an unprotected ground in any transient

scenario with a factor of safety. Furthermore, a membrane with a low magnetic susceptibility

shall shield each conductor to prevent electromagnetic interference with proximate equipment.


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Finally, each conductor shall be spatially separated from each other to prevent cross-talk. If this

spatial separation is not possible, then additional shielding shall be used to mitigate the risk of

arcing and cross-talk. Regular inspections of this insulation shall occur. This insulation shall be

weather resistant and able to last the lifetime of the switchyard under elevated-severity

weather conditions.

The switchyard itself receives demand data from the power distributor through the

power-lines themselves using a power-line communication protocol. This protocol operates in

superposition with the power signal, but at a much higher frequency. A wave trap separates

the power-line communications protocol signal from the power signal and sends the power-line

communications signal to the control room for processing.

All components within the switchyard shall be seismically qualified for the region in

which they are installed Furthermore, all components shall have a nominal operation lifetime

that is either greater that the in-service life of the ART25 reactor or designed to be replaced or

refurbished during the operational life of the switchyard. Furthermore, each component in the

switchyard shall be designed so that it is able to withstand any sort of extreme weather

condition that has a reasonable probability of occurring during the lifetime of the switchyard.Furthermore, corrosion resistant materials should be used wherever possible. All bare metal

surfaces shall be painted to further mitigate against corrosion.

Workers entering the switchyard shall be inspected upon entry to ensure that they are

wearing insulated rubber boots and other appropriate personal protective equipment.

Furthermore, personnel at the switch yard shall all be given high voltage safety training.

Furthermore, safety officers shall routinely patrol the switchyard to ensure that no safetyviolations are occurring.

Site Layout

The layout of the switchyard is depicted in the figure below.


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Figure 1 Site layout

The layout of the switchyard is designed so that it can send 25MW of electrical power to the

grid and the station. The generator sends the power to the bus where it can be divided. The

electric bus is connected to the capacitor bank so that the lag is corrected early, minimizing

losses within the switchyard itself. The control devices also connect at the bus, which is

monitored by the control room. The resistor bank is connected to the bus to open and absorb

energy if a transient is experienced, and is connected to a cooling system to extend the life of

the resistors.

The station service transformer is labeled as a step down transformer and is controlled

to take as much power as the station needs. The transformer is cooled to extend its life. It is

sent to an autotransformer where it is regulated within tolerances, and from there it is filtered

and divided to a single phase tap and 3 phase power lines. From there it is sent to the plant

services transmission which also connects to the control room.

From the electrical bus the step up transformer distributes most of the power to the

grid. This is accomplished by regulating it with an autotransformer, being filtered and phase

corrected similarly to the station services power. However the size and amount of components

is increased due to the increase in power flowing through them. The power grid also has a


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wave trap to prevent high frequency feedback into the switchyard from the grid. The

emergency power distribution is used to send power to the plant from the grid in case the

station loses its ability to produce electricity. The power is stepped down from the grid and

sent to plant.

System Components

A more detailed description of individual system components follows.

Distribution Bus

The distribution bus, also called the electric bus, is responsible for distributing power

from the electrical generator to the plant-side, grid-side and resistor banks. It does this by

connecting the conductor leading from the electrical generator to conductors connecting to the

plant-side, grid-side, and resistor banks through CSMs. Furthermore, there are emergency

circuit connectors that connect the distribution bus to the resistor banks and emergency circuit

breakers are installed on each branch of the distribution bus.

The distribution bus has the current and voltage flowing through each branch of it

measured via galvanometers. These galvanometers are fed a stepped-down voltage that is

congruent with their operational parameters via a step-down transformer. The galvanometers

digitize their signal by actuating a rotary encoder. This signal is then sent to the control room

for continuous monitoring. Furthermore, distribution bus temperature is recorded on the

surface of the insulator of the conductors by an infrared pyrometer. The signal from the

pyrometer is also sent to the control room for continuous monitoring.

The conductors in the distribution bus are shielded from cross-talk via magnetic field

shields (such as mu-metal) that are present whenever the conductors are in close proximity to

each other. The entire distribution bus is built inside a weather-proof metal box that has access

hatches built in for easy maintenance. This metal box features elastomer expansion joints to

prevent structural fatigue from the pulsating magnetic fields that are induced by the alternating


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current flowing through the conductors. The distribution bus shall be seismically qualified and

able to withstand any sort of seismic event with a reasonable probability of occurring.

Wave Trap

A wave trap is a device used to trap the high frequency communication signals sent

through the HV transmission power lines. Its purpose is to filter out only the pertinent

communication signals and divert them to the teleprotection panel in the control room (this is

done with a combination of a capacitor and inductor). This is required because substations

communicate through Power Line Carrier Communication (PLCC) systems. These systems do

not depend on telecommunication company networks.

The communication carrier waves are at a much higher frequency than the power

signal. Each of the wave traps is designed to prevent such carrier waves from entering the lines

and affecting station equipment. They are also protected with a lightning arrester in case of

surges.

The design will need to include several of these in order to ensure that unwanted

frequencies are left out of the station machinery. The wave trap shall be seismically qualified

and able to withstand any seismic event with a reasonable probability of occurring.

Insulator

Insulators are important when designing structures to support electrical equipment and

transmission lines. They are designed to insulate and resist the flow of electrical current while

being able to physically support the wires which carry such currents.

The main type of insulator used to support the transmission lines will be suspension

type insulators. These insulators have a number of ceramic discs connected in series with metal

links to form a chain. Each disc is designed for a certain voltage, the greater the line voltage,

the greater the number of discs required. In addition, the chain like linking of the discs allows

for a minimization of stresses via free swinging. This allows for movement of these insulators


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from wind or seismic events, thus being seismically qualified. Such an insulator is also easy to

repair and modulate by simply replacing broken discs or adding on more discs. The insulation

also provides protection to the lines from currents that would come from the tower, meaning

that there is partial protection from lightning.

Lightning Arrestor

Lightning arrestors are electrical protection tools designed to protect electrical

equipment and insulation from switching and lightning surges. These transients of overvoltage

are captured by the lightning arrestors and sent to the earth. It is the first piece of equipment

in electrical substations.

These will be installed on all towers and poles, transformers, circuit breakers, bus

structures and steel towers in a substation. The lightning arrestors shall be seismically

qualified and able to withstand any seismic event with a reasonable probability of occurring

Resistor Bank

The resistor bank is the device that is responsible for dissipating any excess energy or

residual energy in the switchyard. It consists of a set of parallel branches of resistors in series

(see the figure below).

Figure 2 Sample resistor bank layout


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This arrangement of resistors is to ensure that no single resistor has its maximum voltage rating

or maximum current rating exceeded. The resistor bank must have a total resistance that

ensures the power time-constant of the entire switchyard system, upon a loss-of-power

incident, dissipates power at a rate at which the heat flux from the resistors in manageable.

Each resistor shall be cooled using a recirculating cooling oil system. Each resistor is

installed in a coolant oil reservoir. The size of this oil reservoir is such that the oil in the

reservoir can store the entirety of the heat generated by a complete system discharge from

nominal conditions without failure. Under normal conditions, this cooling oil is circulated by a

pump through a radiator. The temperature of the coolant oil and surface temperature of the

resistors are monitored by thermocouples. These temperature readings are fed back into the

control room to provide process monitoring. The temperature is additional fed back to as a

microcontroller that controls the duty cycle of the recirculating cooling oil pump in a manner

such that the resistor in the oil reservoir is kept at its nominal operating temperature.

There are several input conductors to the resistor bank so that if one input conductor

fails, the resistor bank will still be accessible via another pathway. Furthermore, the current

and voltage parameters of each input conductor is monitored by galvanometers and this data isfed back to the control room. The resistor bank shall be seismically qualified and able to

withstand any seismic event with a reasonable probability of occurring

Step-Up Transformer

The step-up transformers steps-up the voltage on the primary side to a higher voltage

on the secondary side. For the power-grid step-up transformers, the voltage is stepped up to a

level that is congruent with the distribution voltage. Fine adjustment of the voltage is achieved

by using the succeeding autotransformer.


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Step-Down Transformer

The step-down transformer is the conceptual complement to the step-up transformer.

The step-down transformer converts a higher voltage on its primary side to a lower voltage on

its secondary side. fine adjustment of output voltage is achieved by using a succeeding

autotransformer.

The step-down transformer is encased in a magnetic field insulator that provides

shielding which prevents the magnetic field of the step-down transformer from interacting with

proximate equipment. The whole apparatus is encased in a weather-proof box. Both the shield

and the box are constructed with elastomeric expansion joints that prevent material damage by

repetitive bending caused by the alternating magnetic field of the transformer.

The step-down transformers shall be installed in parallel with the resistor bank. In this

way, the back-emf caused by an isolation or loss-of-power event will be dissipated as heat in

the resistor banks.

A nominal operating temperature in the step-down transformer shall be maintained by

a placing the transformer itself in a cooling-oil reservoir. The cooling-oil reservoir shall be sized

so that it can absorb the heat generated by a loss-of-power induced back-EMF event and keep

the step-down transformer below its maximum temperature rating.

Current flowing through the step-down transformer shall be monitored by a

galvanometer. The voltage drop across the step-down transformer shall be calculated by

multiplying the current passing through the transformer by the impedance of the transformer

itself as a function of primary and secondary coil temperature. The step-down transformer

itself will be connected to other elements in the system through CSMs and ECBDs. The step

down transformers shall be seismically qualified and able to withstand any seismic event with a

reasonable probability of occurring.


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Emergency Circuit Breakers

The emergency circuit breakers are devices that break the connectivity of a component

to the switchyard or the switchyard from the grid. Circuit breakers are designed to fail open to

protect any component that may be connected to them from transients that may occur while

the breaker is unavailable. The ECBDs shall be seismically qualified and able to withstand any

seismic event with a reasonable probability of occurring

The emergency circuit breakers use a high-pressure pneumatically operated switch to

connect the two sides of the breaker. When the trip signal is given, a solenoid valve retracts

the pneumatic actuator operates and disconnects the two sides of the switch. There is only

enough air in the reservoir tank for a single operation. An onboard compressor keeps the

reservoir tank pressurized. This use of a reservoir tank allows the ECBDs to operate without any

power other than the trip signal. The trip signal itself originates from the control room and is

sent to the ECCBs by a standard insulated control cable.

Emergency Circuit Connectors

The emergency circuit connectors are fast acting switches that connect an element in

the switchyard to the resistor bank so that residual charge in the element can be safely

dissipated. This emergency circuit connector consists of a normally closed switch that is held

open via an electromagnetic clutch. When de-energized, the switch will close and connect the

switchyard element to the resistor banks. The ECCDs shall be seismically qualified and able to

withstand any seismic event with a reasonable probability of occurring


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Connectivity Switching Mechanism

The connectivity switching mechanism (CSM) is a device that controls the connectivity of

an element in the switchyard to another. It works by using a pneumatically actuated high-

voltage, high-current switch to connect and disconnect a conductor between two elements of

the switchyard. Altogether, there are four switches in each CSM: two parallel sets of two series

switches (see the diagram below)

Figure 3 CSM switch layout

In this way, control is only lost if two out of the four switches are unresponsive. Air is

supplied to the pneumatic actuators of these switches via an onboard reservoir that is

connected to an onboard compressor. The onboard reservoir contains enough air so that

several typical power-maneuvers can be performed; this ensures switchyard operability in case

of a loss of backup power incident. Furthermore, the onboard compressors have an externalshaft that can be connected to a gas-powered portable motor that can power the compressor.

The CSM is controlled through a standard electrical control signal. This control signal is

transmitted from the control room to an onboard controller board via an insulated signal cable.

Furthermore, manual control is enabled by using normally-closed solenoid valves on the

pneumatics lines that have a manual-override lever installed. In this way, if there is a loss-of-

power incident, the CSMs can still be operated via these levers.

The entire CSM, except the switches themselves is to be covered in a weather-proof

metal box. This metal box features elastomer expansion joints to prevent structural fatigue due

to movement induced by the alternating magnetic field created by the power moving through


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the conductors. Due to the tendency for the contacts of the switches to arc, these are left open

to the environment. This metal box is grounded so that any arcing to it will be safely arrested.

Arcing at the CSM switches is unavoidable. The switches contacts themselves are

constructed from a thick conductor that is resistant to damage due to electrical arcing and

weathering. The lifespan of the switch contact should be designed so that sum of the

replacement cost over the lifetime of the plant is minimized. Furthermore, the CSM is housed

within an exclusion cage that prevents people and equipment at a safe distance away from any

arcs induced by the CSM. Furthermore, this cage is grounded so that any arcs that do make it

to the cage perimeter can be safely sunk to ground. A mean looking scarecrow should be placed

on the cage to prevent birds from sitting on the cage or nesting in the equipment. The CSMs

shall be seismically qualified and able to withstand any seismic event with a reasonable

probability of occurring

Galvanometers

The galvanometers serve two purposes: monitoring of the voltage on a conductor, and

monitoring of the current on a conductor. The galvanometer is connected to a low-friction

rotary encoder that allows it to respond to events on the same time-scale as a typical power

transient. The signal from this rotary encoder is sent via a standard signal cable to the control

room so that the galvanometer can be continuously monitored.

Voltage measurements require the use a high resistance resistor in parallel with the

galvanometer. Since a high resistance resistor would need to dissipate many MW of power if a

sizable fraction of the plants output were to be passed through it, galvanometers that measure

voltage first have the voltage passed to them stepped-down by many orders of magnitude such

that the power dissipated by the resistor is a quantity that is manageable by a forced-air heat-

sinking system.


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A regular benchmarking program shall be implemented with the galvanometers so that

the accuracy degradation due to spring-force loss in the restoring spring of the galvanometers

can be compensated for.

The galvanometers are connected to the other elements in the system via CSMs in the

input and output sides as well as emergency breakers. Since there are no capacitive or inductive

elements in the galvanometers, a connection does not need to be made to the resistor bank.

The galvanometers shall be seismically qualified and able to withstand any seismic event with a

reasonable probability of occurring

Voltage Stabilizing Autotransformer

The voltage stabilizing (or regulating) autotransformer is a transformer that allows for

differential adjustment of its winding ratios. In this way, the magnitude of the output voltage

can be changed.

A transformer that is rated to the power requirements of its installation (grid, 3-phase,

or single phase power) is installed with a secondary winding with multiple taps. These taps are

connected to the output conductor of the transformer via a mechanical interlock that only

allows for a single tap to be connected to the conductor at a time.

The autotransformer receives a control over a standard signal line from the control

room. This signal is computed by calculating the difference between the demanded voltage

and the output voltage of the autotransformer. The tap that is the closest match to the

demanded voltage is then selected.

The autotransformers are installed such that there is a parallel connection to the

resistor bank. In this way, any back-emf generated by a power transient will have a time-

constant large enough that it does not generate a damaging spike in transformer voltage.


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3. Place ground rods and wells around the substation to better dissipate faultcurrent.

Soil Preparation

The preparation of the soil before the ground rods are inserted aides in lowering the

resistivity resulting in adequate ground resistance. The design will have an initial layer of clay

for a half-metre, followed by five metres of loam and above the loam will be half a metre of

gravel. Lastly a well for any maintenance is to be installed. The well will be slightly covered with

gravel but can be accessed easily by electrical technicians. Using this layering will provide the

most resistivity to ground potential rise and other hazards.

Ground Rod Design

The ground rod design will consist of two conductive copper rods. The average ground

rod used in substations is three metres long. The rods used for this design will be six metres in

length and will be distanced six metres away from each other as well. Doubling the length of

the two ground rods wherever grounding is needed will reduce the resistance by a value of 45%

under uniform soil conditions. A groundwire will be used to connect the the ground rod and

the service ground connection which will be found in the control room.

Capacitor Banks

Filter Capacitor Banks

The filter capacitor banks serve the purpose of removing any fast time-scale power

transients from the system. The capacitors in this circuit should be installed in parallel so that

the current passing through any one capacitor does not exceed the nominal operational

parameters of the capacitor. Furthermore, on the power grid side the capacitors shall be high-

voltage ceramic type capacitors. The parallel branches of the filter capacitor banks shall feature


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a multitude of individual capacitors so that the voltage drop across each capacitor is within the

maximum voltage parameters of the individual capacitors.

The filter capacitor bank shall be connected to other elements in the system through

CSMs in series with ECBDs. The shall be an ECCD that connects the filter capacitor bank to the

resistor bank. In the event of an isolation event or excess power transient (that has a timescale

that is within the resolving time of the ECCD), the ECCD will drain the filter capacitor bank to

the resistor bank.

Figure 4 Capacitor bank layout

Voltage and current shall be monitored entering and leaving the filter capacitor bank

and fed back to the control room. Furthermore, a regular maintenance program shall be

implemented in which the operational parameters (time constant, frequency response, etc) of

the individual capacitors in monitored for drift. The filter capacitor banks shall be seismically

qualified and able to withstand any seismic event with a reasonable probability of occurring

Phase Angle Adjusters

The phase angle adjusters adjust the phase angle of the incoming power to match the

demanded power phase angle. A phase angle adjuster shall be provided for each phase of

power being supplied to it. The phase angle adjusters accomplish this by a series of variable

capacitors that are in series with a series of variable inductors. The number of variable

capacitors and variable inductors is determined by the maximum voltage rating of each

component; enough elements should be put in the series so that the maximum voltage rating


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of each component is not exceeded. furthermore, this series of series of variable capacitors and

series of variable inductors shall be in parallel with further series of series of variable capacitors

and series of variable inductors such that the maximum current rating of each component is not

exceeded. See the diagram below for clarification.

Figure 5 Prototypical phase angle adjuster

These variable capacitors and variable inductors shall be controlled by actuators based

on a control signal from the control room. The control signal shall determine the positioning of

the variable capacitors or inductors such that it alters phase angle of the output power so that

it is congruent with the demanded power output angle. The input and output voltages and

currents of the phase angle adjusters shall be monitored by galvanometers and the signals from

these galvanometers shall be fed back into the control room to compute the error value of the

phase angle adjuster system.

Each of the variable inductors shall be wired up in parallel with the resistor bank so that

the back-EMF time constant is large enough that the maximum voltage rating is not exceeded

during a loss-of-power transient. Furthermore, the variable capacitors are connected to the

resistor bank via an ECCD. In the case of an isolation event or an excess power transient that

can be intercepted within the operational-time scope of the ECCD, the ECCD will trip and safely

drain the charge of the capacitors to the resistor bank where it will be dissipated as heat. The

phase angle adjusters shall be connected to the rest of the system through CSMs and ECBDs.The phase angle adjusters shall be seismically qualified and able to withstand any seismic event

with a reasonable probability of occurring


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Emergency Backup Power Redirection Bus

The emergency backup power redirection bus redirects power from the grid to the plant

power supply systems in the event of a loss-of-power incident. It does this by stepping down

grid voltage to the plant distribution voltage with three phase power. A single phase of this

three phase power is the taken off to distribute power to the single phase power systems. The

emergency backup power redirection bus can also accept power from the emergency backup

power systems.

Upon a loss-of-power incident, ECBDs fire and disconnect the plant power supply from

the electrical generator. The emergency backup power redirection bus then switches on to

supply power from the electrical grid to the plant itself. If there is no power available in the

electrical grid the redirection bus will switch again to take power from the backup power supply

systems.

Output Monitoring

Output current and voltage are continuously monitored on both the plant-power side

and grid-power side. This data is recorded in the control room and fed to the digital control

computer so that it can adjust the autotransformers and phase angle adjusters so that the plantoutput is congruent with the grid and plant demands. Furthermore, CSMs are placed between

the switchyard and each output so that the outputs can be disconnected if the need arises.

Digital Control Computer

All component parameters such as temperature, current and voltage will be input into a

centralized digital control computer. This digital control computer will be housed in a

seismically qualified air conditioned room; installed with an uninterruptable power supply to

prevent disruptions due to loss-of-power incidents; and, mounted on a spring table to prevent

damage due to seismic events


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This digital control computer can either be set in manual or automatic mode. In manual

mode, the switchyard is controllable by a human operator at a control panel. In automatic

mode, the switchyard responds programmatically to system demands.

The digital control computer shall take inputs from the grid operator via the power-line

communications protocol. The digital control computer shall output all of the switchyards

parameters to the reactor control room via a data link so that the reactor control room

operators can see what is happening in the switch yard.

Site Features

The foundation of the switchyard shall be made of steel-reinforced concrete. The

concrete pad will be 110x 70 m and shall be built on a slight grade so that water is able to drain

off it.. Concrete foundations below ground level provide an excellent means of obtaining a low-

resistance ground electrode system. Since concrete has a low resistivity a rod embedded within

a concrete encasement gives a very low electrode resistance compared to most rods buried in

the ground directly . It is possible to use the reinforcement rod as the conductor of the

electrode by ensuring that an electrical connection can be established with the main rebar of

each foundation. The size of the rebar and the bonding between bars of each concrete member

must be done so that ground fault current will not cause excessive heating, otherwise such

heating may weaken the concrete member and cause it to fail.

The use of Ufer grounds to turn the concrete foundation into a grounding electrode

means there are some factors to keep in mind. One of these factors is steam. Moisture in the

concrete may turn into steam if a high fault current such a lightning surge or heavy ground fault

occurs. This expansion of the water content in the concrete can produce cracks and damage the

concrete. Another factor to be concerned about is possible corrosion of the rebar when an AC

current flows through it. Corrosion would cause the rebar to expand and produce cracks in the

concrete. Damage to the concrete can be minimized by limiting the duration of the fault current

flow or providing a path from the rebar through the concrete to an external electrode.


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Fencing

There will be a metallic security fence around the perimeter of the switchyard. Like

every other structure the fencing will be grounded in the event of arcing, lightning strike or a

power line snapping and falling on the fencing. The fencing will enclose any part of the

switchyard which is open to the air, contains live equipment which is not encased and the

control building, with a fence that is at least 1.8m in height. The fence will be topped with

barbed wire to keep intruders out. There will be gates to allow entry to the switchyard located

along the fencing. The gates shall not come into contact with the frame or enclosure of any

electrical equipment when fully opened. The gates and fencing shall have high-voltage warning

signs to inform people of the danger of the site. The gates like the fencing will be grounded.

Fire Protection

There are a variety of potential causes of fires in a substation so the fire protection

measures must be robust. An automatic fire suppression system will serve as active fire

protection by detecting fires and spraying an extinguishing agent such as carbon dioxide into

the hazard area. A secondary water sprinkler system will douse the fire in the event that theprimary suppression system fails. Fire protection walls and barriers will serve as passive fire

protection by separating the components of the switchyard to prevent fire from spreading.

There will be self-closing fire doors in the fire walls to eliminate the possibility of fire spreading

due to human negligence. A separation distance of 10-15m from trees or any vegetation will be

maintained to reduce the risk of damage from external fires. Gravel will be used to cover this

separation area to prevent weeds from growing. The main source of flammable material in a

switchyard will be the oil used for cooling the transformer and the resistors, to minimize therisk from these catching fire all the fuel sources shall be separated from each other.

Site Grading

For site grading we will perform a soil report of the proposed sites to test for stability,

shearing strength and sloping of the site. The site will be on higher ground and at a very slight


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grade to minimize the risk of water pooling around the site and allow for easy drainage of water

away from the site. In location one the proximity of the lake allows for drainage to be diverted

into the lake and avoid disturbing the environment.

There are two sites being considered for the ART25. Location one is close to the lake

and the terrain consists of lots of sand and loose rock. There does not appear to be good

foundation rock at location two. For location one, bedrock is near the surface providing for a

stable site. In addition, there is reasonable room for large scale helicopters and small air

transports to land. Of these two locations, location two is a better site to build the switchyard

on.

A surface water drainage system shall be provided to deal with run-off from the concrete pad

and buildings. The run-off will be diverted into the lake to prevent it affecting natural drainage

in the area . Oil interceptors shall be installed to protect the surface water from pollution by oil

leakage from switchyard equipment.

Environmental Impact

The Switchyard is composed of electrical equipment and wiring, and therefore does not

produce any air pollution. Grounding, lightning arrestors, and insulation will protect the

surrounding area from any power surges. Construction and maintenance will cause a minimal

impact on the environment since it is a relatively small system and the parts are easily

replaceable. Noise pollution from the transformers poses the biggest concern regarding the

environmental impact.

Review of Design Requirements

Below is a review of the design requirements as they are listed in the design requirements

document. The congruence of our design with each design requirement is analyzed.


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Functional Requirements

The Switchyard shall admit all electric power coming from the Main-OutputTransformer.

o The conceptual design admits power coming from the electrical generator. If themain-output transformer (IE some sort of isolation transformer installed on the

electrical generator to interface between the electrical generator itself and the

switchyard) is a device on the electrical generator then the conceptual design

produced meets this requirement.

The Switchyard shall transmit electric power to the power grid.o The conceptual design transmits electrical power to the power grid through the

power-grid side of the switchyard

The Switchyard shall be controllable from a control room.o All the instrumentation readings arrive at a central control room. All the control

signals are sent from the control room. In this way, the switchyard is

controllable from a control room.

The Switchyard shall contain the automatic switching mechanisms (such as fuses orcircuit breakers) that inter-connect the station and power grid.

o The CSMs placed at the external interfaces of the switchyard interconnect thestation to the power grid. This requirement has been met.

The Switchyard shall be able to supply electric power to the station in the event of anoutage.

o The emergency power redirection bus enables both grid power and backuppower be redirected to power both the three phase and single phase plant

power systems. If an outage does occur, this redirection bus provides electrical

power to the plant. This design requirement has been met.

Performance Requirements


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The Switchyard shall transmit 3 phase AC power to the grid, offset at 120 degrees tomaintain a consistent flow of power to the grid.

o The switchyard transmits the three phases generated by the electrical generatorto the power grid. This requirement has been met.

The Switchyard shall be backed by redundancy by utilizing extra lines and double busbar setups.

o The critical components in the switchyard have multiple conductors leading toand from them. In this way, this requirement has been met.

The Switchyard shall have a lifetime of at least that of the ART25.o Each of the individual components in the switchyard have a lifetime that is

greater than that of the ART25 reactor or are able to be easily replaced (such asthe CSM contacts) within the operational life of the switchyard. This

requirement has been met.

The switchyard shall be able to accept continuous 30MWe electric power (normaloperations output 25MWe).

o The switchyard is designed to continuously transmit 30MWe of electrical powerfrom the electrical generator to the grid. This is accomplished by using

components in parallel and series so that the power across each component is

within its operational parameters. This requirement has been met.

The Switchyard shall be able to continuously operate automatically. This impliespersonnel free operation under normal operating conditions.

o The digital control computers allow for hands-free operation of the switchyard.This requirement has been met.

Safety Requirements

The Switchyard shall be seismically qualified.


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further protected from extreme temperature conditions. This requirement has

been met.

The Switchyard shall be protected against direct lightning strikes.o The lighting arrestors, grounding of components, and ECBDs protect the system

against direct lightning strikes. Furthermore, the filter capacitor banks protect

the system from power transients with a time scale congruent with a lighting

strike. In this way, this requirement has been met.

The Switchyard shall have a grounding mechanism emplaced to deal with over-currenttransients and over-voltage transients.

o Over-current and Over-voltage transients are dealt with by isolating systemcomponents and sinking them to the resistor banks. Furthermore, theautotransformers can handle minor power transients. This requirement has

been met.

The Switchyard Shall be able to admit electric power to station service transformerfrom auxiliary backup generators if necessary.

o The emergency backup power redirect bus is able to redirect power from thebackup power service to the station power supplies. In this way, the essential

functionality of this requirement has been met.

The fence of the switchyard shall prevent intrusion from animals or humans.o The fence installed at the perimeter of the switchyard prevents unauthorized

intrusion by humans or animals. Without subversive measures, the only way

into the site is through the entrance gate. This requirement has been met.

The Switchyard shall be resistant to corrosion.o Corrosion resistance is provided by three measures. First, corrosion resistant

materials such as stainless steels are used wherever possible. Second, all bare

metal surfaces are painted to prevent any initial corrosive attack. Finally much

of the equipment is housed in weatherproof boxes that prevent the ingress of

water. This requirement has been met.

The Switchyard shall be well insulated to prevent arcing.


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o All the conductors in the switchyard are insulated, spatially separated, andshielded where possible. Where this insulation is not possible, and exclusion

cage is installed. This requirement has been met.

Client Requirements:

The Switchyard shall be constructed above ground.o The switchyard is constructed above ground, on a grade. This requirement has

been met.

The Switchyard shall transmit 25MWe to the power grid.o The switchyard is able to transmit 30 MWe to the power grid. Since 30 MWe is

greater than 25 MWe, this requirement has been met.

Reliability and Maintainability Requirements

The Switchyard shall undergo maintenance at least once per year.o The continuous inspection routine performs maintenance on any system

components if they drift too far off from their nominal operating values. The

once per year aspect of this requirement is unfounded. Nevertheless, the intent

of this requirement is met.

The Switchyard shall have voltage and current monitors to facilitate inspection.o The voltage and current measurement devices implemented in each system

component. The readings from these instruments are recorded in the control

room. Inspection personnel can be given access to these records to facilitate

their inspection routines. This requirement has been met.


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Cost Requirements

The Switchyard shall be financially reasonable.o No new technology needs to be developed for this switchyard. Standard, off-the-

shelf components can be used for many of the components. A priori, this

enables the switchyard to be financially reasonable. This requirement has been

met.

Environmental Requirements

The construction, maintenance and operations of the Switchyard shall not leave asignificant environmental footprint.

o There are no reaction chambers or effluent streams leaving the switchyard. Theonly environmental impact is that which is created by its construction and

production of replacement operating equipment. A priori, there is no significant

environmental impact. This requirement has been met.

The Switchyard shall not be loud during normal operations.o The switchyard has no large-scale motors or other devices that produces

elevated noise levels. There will be some hum due to the alternating magnetic

fields in the transformers, but this is hardly what one would consider loud. This

requirement has been met.

The insulation used in the Switchyard shall not create significant pollution problems.o Due to its lifespan, there is minimal atmospheric pollution created by the

degradation of the insulation. The insulation used in the switchyard can be

disposed of in a method that traps any leaching material. In this way, the

pollution created by the insulation is manageable. This requirement has been

met.


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Human Factor Requirements

The Switchyard must be easy to operate and easy to access for inspection.o The centralized control room and site layout provides easy control of the

switchyard and easy access for inspection. This requirement has been met.

The Switchyard is remotely operated from the control room and easy access is grantedfor routine inspections and maintenance.

o All control signals originate from the control room. The layout of the switchyardenables easy access. This requirement has been met.

Workers given access to the Switchyard shall be outfitted in safety gear duringoperations.

o Compliance with personal protective equipment policy is ensured at the gate tothe switchyard. This requirement has been met.

Workers shall wear insulated safety gear when working within the switchyard toprevent any shocks from the electrical systems.

o The regular safety patrols will ensure the personal protective equipment policy isfollowed by employees working in the switchyard. This requirement has been

met.

Layout Requirements

The switchyard must be placed between the Main Output Transformer and PowerGrid.

o The main output transformer (step-up transformer) is located within theswitchyard and has transmission lines to the grid. The intent of this requirement

has been met.


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Assumptions

Since all information on the other systems was not presented or given in design

documents it is necessary to make and state assumptions in order to do a proper analysis of the

switchyard system.

Turbine Generator Assumptions

While the ART25 Turbine Generator describes in detail what the turbines operating

conditions are the only given as 25MWe output at either 50 or 60Hz. For an electrical system

this knowledge is inadequate to design a switchyard around. The assumptions made are:

1) The turbine generates AC power.

2) The stator is divided into three equally sized regions at 120 to each other.

This will generate three phase power, as opposed to a single phase, which will

increase efficiency as one phase is always peaking.

3) The stators are connected in a wye configuration, as opposed to a delta configuration.

This will allow one phase to be disconnected without disconnecting the other

two phases. Delta configuration is also not regularly used in practise (Rizzoni, 2007).

4) The output potential of the turbine generator is a typical 18kV (Rizzoni, 2007).

Bibliography

(2013).ART25 Reactor Project Design Information Package.Advanced Reactor Technologies.

Chief Engineer Harvel. (2013). Filing Numbers.Advanced Reactor Technologies.

Dave, C. E. (Aug 27, 2010). Conceptual Design Projects for ART25 BOP.Advanced Reactor

Technologies.

Dr. Glenn Harvel, Chief Engineer. (2013). Phase IIIa conceptual designs.Advanced Reactor

Technologies.

Electrical4u. (n.d.). Types and Operation of SF6 Circuit Breaker. Retrieved from

http://www.electrical4u.com/types-and-operation-of-sf6-circuit-breaker/


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Julia. (2010). Site Characteristics of Blue Valley Mineral Deposit.Advanced Reactor

Technologies.

Krishna, B. (n.d.). Substation Overview. Retrieved from

http://www.authorstream.com/Presentation/balu56208-1905811-substation-view/

Pansini, A. J. (2005). Guide to Electrical Power Distribution Systems.CRC Press.

Pansini, A. J. (2005). Power Transimssion and Distribution .CRC Press.

Rizzoni, G. (2007). Principles and Applications of Electrical Engineering.

5000 electrical switchyard design report group 8 final

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