sistema de excitacion (ingles)

8/9/2019 Sistema de Excitacion (Ingles)

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Table of Contents

1 BRUSHLESS EXCITATION SYSTEM .............................................................................. 1

1.1 General .......................................................... ................................................................. ...................................... 1

1.2 Rectifier Wheel ........................................................ ................................................................. ........................... 1

1.3 Field Breaker ........................................................... ................................................................. ........................... 1

1.4 Initial Excitation Equipment ........................................................ .............................................................. ........ 2

1.5 Automatic Voltage Regulator ................................................................. ............................................................ 2

1.6 Control and Instrumentation ................................................................................................ ............................. 2

1.7 Board and internal wiring ............................................................................................ ...................................... 2

2 SPARE PARTS ...................................................................................................................... 4


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1 BRUSHLESS EXCITATION SYSTEM

1.1 General

The brushless excitation system includes an AC exciter, permanent magnet generator,

rectifier wheel, field breaker, discharge resistance, field flashing, automatic voltageregulator microprocessor, protection, instrumentation and control; wiring, boards and all

necessary accessories.

The excitation system must be designed with a power system stabilizer (PSS).

The AC feeding to the excitation system has to be taken directly from the permanent

magnet generator terminals.

The excitation system must be capable to continuously supply the maximum necessary

excitation current to produce 110 % of the rated power with a nominal power factor and

110% of the rated voltage at the nominal frequency of the generator; plus a 10% of

additional capacity.

The ceiling voltage should be less than 200% of the field rated voltage and no lower

than 400% of the excitation voltage in vacuum. The excitation system must be capable

to operate at ceiling voltage for at least 10 seconds, without causing any damage, follow

the continuous operation of the generator at nominal power.

The system must be able to control generators nominal voltage in all its operating

conditions facilitating joint control. The precision of the voltage regulator should be at

least 0.5%.

The excitation system must be capable to provide negative ceiling voltage to force the

field in case of load rejection.The excitation system should be able to withstand atmospheric discharges, overvoltage

generated by switching operations and dynamic overvoltage to which the generator may

be subjected.

The usage of crowbar or equivalent is going to be necessary for protection against

overvoltage.

The excitation system must have limiting functions, and necessary functions.

The excitation system should be capable to operate in manual mode, from cero until

reaching the total voltage of the generator for testing purposes.

1.2 Rectifier Wheel

The wheel bridge rectifiers must be silicon controlled and the number of bridges must

be such that there is always a redundant bridge.

The equipment must be cooled by forced air. To achieve this, fans need to be installed,

with 100% redundancy.

The rectifier units of each bridge must be demountable for maintenance.

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Field BreakerOne DC circuit breaker should be supplied in the field circuit to ensure a definitivedisconnection of the field from the power supply and to discharge the energy from the

field circuit in case of existence of a severe internal damage, a tree-phase short-circuit at


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the generator. The energy from the magnetic field must be dissipated via a nonlinear

discharge resistance that should be connected to the field circuit during such operation.

The circuit field circuit breaker must be removable through appropriate tools when it is

opened for maintenance.

The field switch breaker should be equipped, with two (2) trip coils in 125 V DC.

1.4 Initial Excitation Equipment

The equipment for the initial excitation (field flashing) must be obtained from the 400 V

AC auxiliary system and alternatively from the 125 V DC system. When batteries for

the initial excitation are used, the overvoltage protection equipment must be provided as

part of the excitation system.

1.5 Automatic Voltage Regulator

The excitation system will be controlled by an Automatic Voltage Regulator (AVR)

two channels with digital microprocessor, completely redundant. The excitation controlshould be suitable to work in automatic and manual mode. In case of fail in the

automatic mode, must be transferred to the manual mode.

The AVR should have the following additional characteristics:

a)

Reactive power control devices to ensure proper distribution load during

simultaneous operation of the generators;

b) Power factor regulator;

c) A device that adjust the minimum excitation limit with characteristics that matches

with the generators capability curves;

d) Adjustable device for maximum excitation limit;

e) Controller to facilitate the mode transition from Automatic to Manual and vice

versa;

f) Voltage drop compensator across the line;

g)

Power stabilization system (PSS);

h) Field current control.

1.6 Control and Instrumentation

The excitation system must allow local and remote control. It must be able tocommunicate with the unit control system via the field bus (Profibus DP). The circuit

trips must be wired.

The excitation system should have an adequate local panel to display the main variables.

1.7 Board and internal wiring

All the equipment of the excitation system must be properly installed in metallic dust

proof panels.

The power cables must be supplied and installed for all existing connections between

excitation system boards and other equipment. Control and instrumentation cables shall


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be provided and installed for connection between the individual components and

excitation system boards.


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2 SPARE PARTS

The contractor shall provide at least the following spare parts suitable for the excitation

system:

a) Rectifier

-

One (1) complete power thyristor bridge;

- Three (3) sets of thyristor for a bridge;

- Three (3) sets of power fuses for a bridge and indicators;

- Two (2) cooling fans;

b)

Automatic Voltage Regulator

-

Two (2) modules of each type;

-

Two (2) relays of each kind;

-

Two (2) transducers of each type;

- Two (2) power stabilization systems;

- Two (2) sets of signal lamps and fuses;

c) Auxiliary Relays;

- Two (2) timing relays of each type;

- Two (2) auxiliary relays of each type;

-

Two (2) protection relays of each type;

-

Two (2) amplifiers and pulse transformer;

-

Two (2) circuit breaker of each type;

- Two (2) sets of diode (blocking diodes);

d) Field switch

- One (1) complete field switch;

- Two (2) sets of main contacts and arcing, fixed and mobile;

- Two (2) discharge resistors;

-

Two (2) closing coils;

-

Four (4) trip coils;

- One (1) spring charging motor;

-

One (1) set of crowbar components;

e) Field Flashing

- One (1) field flashing transformer;

- One (1) field flashing bridge rectifier;

-

One (1) field flashing contactor;

- One (1) field flashing resistance;


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All the spare parts must be electrically and mechanically identic to its corresponding

equipment, must be adjusted and calibrated if necessary and they have to be properly

stored and labeled, ready for long term storage. A list with all the spare parts and

specifications must be provided.

Also it should include the scope of provision of all necessary tools for operation and

maintenance.

sistema de excitacion (ingles)

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