power equipment center application guide - siemens
TRANSCRIPT
Definition
A PEC is a prefabricated, modular electrical/instrument enclosure. As a self-contained unit, it is a completely assembled enclosure manufactured entirely at the factory. The most common designs employ self-framing interlocking wall and roof panels attached to a structural steel base.
Equipment enclosed within a PEC can include:
Low- and medium-voltage switchgear
High-voltage gas-insulated switchgear (GIS)
Low- and medium-voltage motor control centers
Protective relay panels
Remote terminal units
Instrument control panels
Distributed control systems
Heat trace panels
Uninterruptible power supply systems
Supervisory control and data systems.
Power equipment center application guide
Introduction
For many years, the petrochemical industry has utilized power equipment centers (PECs) to house electrical equipment. Many utility and industrial customers are now utilizing PECs for their equipment as well. This document explains the benefits of PECs and compares them to conventional site-built technology for housing outdoor electrical equipment.
The Siemens PPS facility has been manufacturing PECs since 1988 with installations across many industries.
Figure 1: Modular
PEC enclosures
Figure 2: Typical wall, roof and ceiling panel
for Siemens interlocking panel
(type SIP) PEC
16” (406 mm)
2.9” (74 mm)
2
A PEC is designed and manufactured in accordance with a number of rigorous industry standards. Additionally, a PEC must be built to comply with local building codes.
A partial list of industry standards met by PECs built by Siemens:
ASCE/SEI 7-05 - Minimum Design Loads for Buildings and Other Structures
NFPA 70 - National Electrical Code®
AWS D1.1 - Structural Welding Code
ASTM A-525 - Standard Specification for Sheet Steel with Galvanized Coating to G90 Standards
ASTM A36 - Standard Specification for Carbon Structural Steel
AISC Manual of Steel Construction Allowable Stress Design
IBC - International Building Code.
Standards
Figure 2: Typical Siemens interlocking panel (SIP) PEC construction detail
A
C
D
E
Item Description
A Roof trim
BWeatherproof interlocking
panels
C Polycarbonate viewing window
D Panic bar hardware for safety
E 1/4”(6 mm) floor plate
FStructural steel support; sized
for weight and strength
G C-channel supports
H Perimeter base
I Interior wall liner
J 3” (76 mm) insulating space
KInterior interlocking ceiling
panels
B
B
F
GH
I
J
K
3
Roof system
Roof panels are typically constructed from 18-gauge minimum, powder coated, galvanized steel (G90) that are formed to provide an interlocking system. Roof panels are supplied in a single continuous length from eave line to ridgeline and designed for 30 psf loading. Higher roof loads can be achieved as required.
Roof structures can also be designed for roof mounted HVAC units, entrance bushings and overhead bus supports.
Figure 4: Roof - section view through the top wall cap provides a typical roof and ceiling section view detail.
Wall system
Wall panels are typically constructed from 18-gauge minimum, powder coated, galvanized steel that are formed into an interlocking system. Interlocking 3” (76 mm) exterior wall panels are arranged on 16” (406 mm) centers and provide 90 MPH allowable wind loading. Higher wind load ratings can be provided as required.
Interior wall liners and various insulation levels can also be provided.
Figure 5: Section view through an insulated wall and Figure 6: Typical wall-floor connection on page 5 reveal construction details of the interlocking wall and the connection of these walls to the PEC floor.
Construction
Base structure
The steel supporting skid is fabricated from standard AISC shapes using ASTM A36 steel. Provisions are made for lifting the PEC for shipping and erection. The floor plate is ASTM A36 material and is typically designed for 250 pounds per square foot (psf) loading. All structural framing members are cleaned by metal-bead blasting and then painted with a protective coating. The PEC base is typically structural steel perimeter members rigidly braced with structural steel cross-members for installation on a concrete foundation or piers.
Figure 3: Typical skid construction details depicts such a base design.
Figure 3: Typical skid construction details
A
Item Description
A Appropriately sized and spaced cross members
B Appropriately sized and spaced supports
C Appropriately sized perimeter channel
D 1/4” (6 mm) plate
E Lift point
B
CD
D
E E
Length
Width
Figure 4: Roof - section view through the top wall cap
Item Description Item Description
A Fascia E Sloped roof panels
B Top and bottom skip weld F Ceiling panel
C #14 Tek screws G Drip shield
D Wall panel H12-gauge galvanized wall cap
roof and ceiling support
AAC
B
B
D D
C
G
E
F
H H
4
Other construction features
Typically, PECs are provided with interior and exterior lighting, heating, ventilation and duplex receptacles.
PECs can also be provided with air conditioning, humidity control and pressurization/purge systems (NFPA 496).
Additionally, most features available in a site-built facility are available in a PEC; including offices, bathrooms, communications rooms and battery rooms.
Figure 7: Typical PEC equipment layout including lighting on page 6 illustrates some of these details.
Resistance to environments
The interlocking panel design provides a barrier against water entering the PEC by providing two 90° bends at seams between the exterior and interior walls of the PEC. Additional weatherproofing is also provided to ensure enclosure integrity.
After assembly of the wall system, all seams are sealed with an industrial grade silicone sealant. Roof sealing putty is used at all wall-to-roof joints and at joints on peaked-roof enclosures. All roof panels are also individually sealed with silicone sealant.
The paint system consists of surface preparation, primer on the base steel, underside coatings, finish paint or coatings and sealant. The finish coat on base steel is typically epoxy-based. For wall, ceiling and roof steel, an electrostatically applied and thermally set polyester powder coat finish is used. Each provides outstanding resistance to chemicals, moisture and abrasion.
These coatings are highly resistant to the deteriorating effects of many acids, alkalis, solvents, greases, oils and other active chemicals. Other coating systems can also be considered.
The resulting enclosure can be designed for extreme ambient temperature and humid environments, ranging from minus 40 °C to 50 °C, while allowing the use of lower cost indoor types of switchgear and electronic equipment.
Grounding system
The PEC is furnished complete with suitable factory installed grounding provisions. Through appropriately sized ground buses and bonding jumpers, all electrical equipment enclosure frames and ground buses are in turn bonded to the building frame. Four two-hole ground pads are provided, with one located at each corner of the PEC exterior. Two of the ground pads are bonded to the interior ground bus.
A separate ”quiet” or isolated instrument ground bus can also be provided.
Figure 5: Section view through an insulated wall Figure 6: Typical wall-floor connection
Item Description
A 3” (76 mm) fiberglass insulation
B Inner wall
C All seams silicone sealed
D Outside of interlocking wall panels
E #14 Tek screws
A
32” (813 mm)
B
C D E
E
3” (76 mm)
Item Description
A Interior wall
B1/4” (6 mm) floor plate
C Perimeter channel
D #14 Tek screws
D
A
B
C
3” (76 mm)
5
PEC application benefits
One of the significant advantages of the PEC alternative is minimal field erection and commissioning time and expense. All equipment is interconnected and tested before shipment from the factory, including switchgear, DCS systems, power panels, heat trace panels, lighting panels, HVAC and battery systems. In the case of conventional buildings, the purchaser or contractor must coordinate and provide field labor to install, interconnect and test all equipment on site.
With the PEC option, a major part of the engineering, drafting and coordination is transferred to the PEC manufacturer under one purchase order early in the project. Whereas, even a small site-built facility has all the elements of a major project requiring project management and coordination. Furthermore, for a conventional building project, a series of purchase orders will be required that can complicate the coordination effort. Numerous meetings for evaluation, review and coordination are necessary, and require additional allocation of the purchaser’s resources.
Engineering, fabrication and planning can proceed while waiting for equipment arrival at the PEC manufacturer’s location. Experience has shown that up to four times the man-hours must be allotted for site equipment installation because of the additional work done in the field, in contrast to a PEC which arrives complete, pre-tested and ready for installation.
PECs can be installed on field erected piers which allows for them to be elevated to avoid flooding ‒ an advantage for installations near bodies of water or rivers. Having the PEC located on piers also provides the ability to install cable tray and bus duct systems below the building without the need for ground excavation. PECs can also be relocated and are not considered permanent structures as conventional buildings are.
With a site-built facility, commercial warranties may be affected by staggered lead times that do not run concurrently with the overall system commissioning date.
Applications
Application of a PEC is usually compared with conventional outdoor electrical/instrument enclosures such as concrete block facilities and sheltered-aisle switchgear. Evaluation is centered on the issues of effective application, initial installation costs and total life cycle costs.
Specific construction and procurement factors provide the basis for a more detailed technical and commercial comparison of alternatives.
PEC vs. conventional building
PECs are primarily used in applications that have traditionally favored electrical rooms constructed at the site utilizing conventional construction techniques. Table 1: Comparison of PECs and conventional site-built enclosures on page 8 elaborates the advantages of a PEC compared to the most common alternative, a concrete block building.
Item Description
A 10” (254 mm)
B 4’ (1.2 m)
C 7’ (2.1 m)
D Light
EMedium-voltage
switchgear
F 15” (381 mm)
G 3’ (914 mm)
H Fire extinguisher
I Electric unit heater
JUtility transformer (transformer and
panel)
K 8” (203 mm)
L 2’ (610 mm)
M 14’ (4 m)
D
Figure 7: Typical PEC equipment layout including lighting
D D D D
D
D
D
E
H I
J
Rear access
31’ (9.4 m)
9’ (2.7 m) auxiliary equipment area
A
G
K
L
M
F G G G G G G G
A
B
C
6
PEC vs. NEMA type 3R sheltered-aisle enclosure
Most major switchgear suppliers, including Siemens, offer a line of sheltered aisle in single-row or double-row arrangements that typically comply with NEMA 3R requirements for outdoor installation.
Single-row installations consist of a lineup of outdoor switchgear adjacent to a weatherproof walk-in aisle. The overall design provides weather protection and good economy of space, but is limited in application flexibility and room for auxiliary equipment.
Table 2: Comparison of PECs and NEMA 3R sheltered-aisle switchgear on page 9 provides a more detailed comparison of PEC construction and application as an alternative to NEMA 3R sheltered-aisle switchgear enclosures.
Additionally, a PEC provides superior weather protection and can be insulated and air conditioned to protect sensitive electronic equipment. Sheltered-aisle switchgear is limited to the type of non-switchgear equipment that can be housed in the enclosure.
PEC and high-voltage switchgear
Through the use of SF6 gas-insulated switchgear, a PEC can also be used for housing primary (transmission and substation) switchgear. A double-feed station, or H configuration can be housed in a single PEC. This configuration provides enormous space savings, higher reliability and less maintenance than a typical air-insulated substation. All the advantages of a PEC (single-point engineering, procurement, fabrication and testing) are applicable to high-voltage switchgear. In combination with a secondary switchgear PEC, an entire substation could consist of two PECs and transformers.
Special applications
PECs can be designed for high-wind loading (up to 150 mi/h), seismic zone 4 applications and high-snow loading. Fireproofing can be installed on exterior walls to protect switchgear from transformer failures. Special exterior finishes can be provided to better integrate a PEC with the surrounding environment. To eliminate additional facilities, options such as offices, battery rooms, bathrooms or maintenance rooms, can be added within a PEC.
With most PEC installations, the warranty period for all the equipment inside the PEC will last for a predetermined number of months after shipment from the PEC manufacturer or from time of commissioning, whichever occurs first.
Also, shipping time differs for each type of electrical equipment being installed. The total shipping time for PECs is only four to six weeks longer than for individually procured indoor equipment of the same type.
Finally, the sum of individual equipment prices is not typically as low as equipment purchased as a package from a single supplier.
Buying integrated PEC systems from one supplier in lieu of the conventional “Built on site” type of buildings can result in coordination simplicity, application flexibility, cost savings, quicker delivery and installation.
Figure 8: Type Siemens interlocking panel (SIP) PEC with HVAC system
7
Table 1: Comparison of PECs and conventional site-built enclosures
Feature PEC Conventional site-built construction
Major electrical equipment Same Same
SourcingManufacturer responsible for all equipment inside the
PECSeparate solicitation, analysis (and often) sourcing of switchgear, building, battery systems, bus duct, etc.
Design engineeringComplete package designed and engineered by
manufacturerPurchaser must design and engineer
ConstructionVariety of materials, depending on application
environment and structural requirements including galvanized steel, stainless steel and aluminum
Typically concrete block
Foundation Minimum foundation (for example, curb or pier type)Requires full slab foundation with relatively large
stem walls and footings
BaseSelf-supporting; allowing all equipment to be factory
leveled before shipmentPurchaser provides channel base and grouting for
leveling all equipment
AccessCan be provided with hinged switchgear doors in rear
for access to terminations (rear aisle inside PEC not required)
Must be 25 percent to 40 percent larger than an equivalent PEC to permit access to switchgear bus
area and terminations
Internal wiring Factory wired complete with wiring schematicsJobsite interconnection of control wiring in addition
to major equipment
Main bus Coordinated by manufacturerPurchaser coordinates the match up of main buses for
different types of equipment
Bus duct from transformers Checked for ease of assemblyPurchaser coordinates and assembles bus to
switchgear in field for first time
Grounding system Integral to PEC Must be planned and built into foundation
External connectionsEasily adaptable to overhead or underground conduit
systemsSlab floor mandates detailed and exact conduit
location; changes are difficult
TestingPEC is factory tested; customer can complete many pre-energization tests before installation. Witness
testing can be performed at one location.
Each type of equipment is tested at different factories. Witness testing requires more time and
travel.
ChangesChanges can be made after functional testing and
inspection in a controlled factory environmentRequires coordination among various trades, often
after initial construction is complete
Receiving, handling and storageArrives ready for installation or secure storage with
minimal preparation
Purchaser must provide for receiving and storing of material and equipment at different times by different suppliers. Often this involves redundant handling for storage, truck to intermediate locations and requires storage to protect from weather, pilferage and other
loss.
Installation Involves minimum number of craftsRequires multiple crafts (for example, carpenters,
ironworkers, cement finishers, bricklayers, electricians - all with foremen and helpers)
ExpansionModular construction results in convenient
expandability as system growsSpace for expansion must be included in initial
installation
Commercial Typically taxed same as weatherproof equipment1
Treated as real estate improvement necessitating higher tax schedule, permits, progress inspections,
bonding and insurance1
Footnotes:1. This is an illustration and does not constitute
tax or legal advice. Please contact a qualified tax consultant to confirm tax treatment of a PEC in your area.
8
Table 2: Comparison of PECs and NEMA 3R sheltered-aisle switchgear
Feature PEC Shelter-aisle switchgear
Major electrical equipment Same Same
SourcingManufacturer responsible for all equipment inside the
PEC and PEC can accommodate various types of electrical equipment
Separate enclosure must be sourced for each type of electrical equipment
Design engineeringComplete package designed and engineered by
manufacturerPurchaser must design and engineer
ConstructionVariety of materials, depending on application
environment and structural requirementsTypically manufacturer’s standard steel construction,
paint and finish
Foundation Minimum foundation (for example, curb or pier type) Same
BaseSelf-supporting; allowing all equipment to be factory
leveled before shipmentPurchaser provides level foundation or piers and
grouting for leveling all equipment
Internal wiring Factory wired complete with wiring schematicsJobsite interconnection of control wiring in addition
to major equipment
Main bus interconnections Coordinated by manufacturer Purchaser completes in field at every shipping section
External connectionsEasily adaptable to overhead or underground conduit
systems
Slab foundations require exact conduit location making changes difficult. Not suitable for overhead
tray installations.
TestingPEC is factory tested; customer can complete many pre-energization tests before installation. Witness
testing can be performed at one location.
All field reconnections require retesting by field personnel
Receiving, handling and storageArrives ready for installation or secure storage with
minimal preparation
Purchaser must provide for receiving and storing of multiple pieces requiring re-assembly. Often involves
redundant handling for storage, trucking to intermediate locations, and protection during storage from pilferage, other loss or lost time due to weather.
Installation Involves minimum number of craftsNEMA 3R construction must be field assembled or
connected to shipping groups
Transom
24’ (7.3 m)
15’ (4.6 m)
75’ (22.9 m)12.7’
(3.9 m)
Shipping limited based on combination of:
Length
Width
Height
Destination.
Dimensions in feet (meters).
Larger sizes available. Consult factory.
4080 Door HVAC
Figure 9: PEC dimensions
9
Summary
A PEC provides the end user with a self- contained, pre-engineered, prefabricated solution to enclosing various forms of equipment, such as switchgear, auxiliary electrical equipment, instrument/control panels, DCS systems, heat trace panels and UPS systems.
Of particular significance is:
The ability to provide rugged, reliable enclosure construction in accordance with established standards
The ability to acquire the complete outdoor electric/instrument equipment package from a single supplier with design and engineering responsibility
The ability to provide complete pre-delivery interconnection and testing, to include switchgear control wiring, lighting transformers, power panels, lighting panels, lighting fixtures, receptacles, exterior lighting, batteries and chargers.
Modular construction from interlocking materials contributes to flexibility as well as cost effectiveness. PECs are designed to reduce engineering, procurement and field costs as compared to other enclosure technologies, without decreasing reliability, maintainability or performance.
Siemens provides a single-source solution for PEC and electrical equipment requirements. No other PEC manufacturer has the range of products and application experience that Siemens can deliver.
The solution
A key advantage of the PEC is the flexibility to provide a variety of equipment (switchgear, relay panels, RTU, supervisory control and battery systems, data logging, event recorders, etc.) installed and interconnected in the same enclosure.
Figure 10: Type Siemens crimp plate (SCP)
10
www.usa.siemens.com/energy
Published by and copyright © 2011:Siemens AGEnergy SectorFreyeslebenstrasse 191058 Erlangen, Germany
Siemens Energy, Inc.6510 Bourgeois RoadHouston, TX 77066-3111, USA
For more information, please contact: Phone: +1 (281) 444-1200Toll-free: +1 (800) 347-6659www.usa.siemens.com/energy
Order No. E50001-F710-A394-X-4A00Printed in USATB 2494T BR 0911.2
All rights reserved. Trademarks mentioned in this document are the property of Siemens AG, its affiliates, or their respective owners.
Subject to change without prior notice. The information in this document contains general descriptions of the technical options available, which may not apply in all cases. The required technical options should therefore be specified in the contract.