Metal Enclosed Bus SystemsTechnical Specification
Technical Specifications
1.0 GENERAL
1.1This specification will establish the electrical and mechanical requirements for the metal-enclosed bus to be used on the project specified.
2.0 STANDARDS AND CODES
2.1The bus systems will be manufactured and tested in compliance with the latest applicable sections of the listed standards and codes. Any exception to this specification must be clearly stated in the suppliers quotation.
2.1.1American National Standards Institute (ANSI - C37.20 & ANSI C37.23)
2.1.2National Electric Code (NEC)
2.1.3National Electrical Manufacturers Association (NEMA)
3.0 SITE CONDITIONS
3.1Ambient air temperature limits -30 degrees C to +40 degrees C
3.2Altitude above sea level _____ft.
3.3Maximum wind velocity _____miles per hour
3.4Ice load _____pounds per square foot
3.5Snow load _____pounds per square foot
3.6Seismic zone_____
4.0 BASIC CONSTRUCTION
4.1General
4.1.1The bus will be non-segregated phase type with either full air space or air/composite design as acceptable. Low impedance busway is unacceptable.
4.1.2Outdoor installations shall be of the non-ventilated, totally enclosed, weatherproof design.
4.1.3Indoor installations shall be of the non-ventilated, totally enclosed, drip-proof or side and bottom ventilated design.
4.2Ratings
4.2.1Maximum Voltage _____kV RMS
4.2.2Basic Impulse Insulation Level (BIL) _____kV
4.2.3Rated Frequency Withstand _____kV (1 min. dry) 60HZ
4.2.4Rated Continuous Current _____Amperes
4.2.5Short Circuit Withstand Current_____KA Asym 167MS
4.2.6Maximum temperature rise is 65 degrees C for silver plated (or equivalent) conductor and 30 degrees C for unplated conductor. Maximum total conductor temperature is 105 degrees C.
4.2.7Enclosure total temperature limit is 80 degrees C.
4.3Conductors
4.3.1Conductors will either be ETP 110 Copper (98% IACS) ASTM Designation B187 or 6101-T61 Aluminum (57% IACS) ASTM Designation B236.
4.3.2Conductors must be of sufficient cross section so as not to exceed specified temperature limits when operated at the rated continuous current and must operate within the temperature limits of the insulation during short circuit conditions.
4.4Bus Joints
4.4.1Contact surfaces of bolted copper joints will be electro-silver plated. Contact surfaces of aluminum joints will be electro-tin plated.
4.4.2High strength plated steel hardware including lockwashers and flatwashers are to be supplied for all bus joints. Belleville spring washers will be used on all aluminum joints.
4.4.3All bus joints will be made with bolts going through the bus conductors and will be uniformity tightened per the manufacturer's torque recommendations.
4.4.4Total cross sectional area of the splice plates must equal or exceed the main bus cross sectional area. Entire contact area of the splice plates will be plated to match the main bus plating.
4.4.5Joint design must allow for the removal of individual bus sections without disassembly of adjacent bus sections. Overlap type joints which do not allow removal of adjacent assemblies are unacceptable.
4.5Equipment Interface
4.5.1Bus duct manufacturer is responsible for design and coordination of connections to associated equipment. Purchaser will obtain necessary interfacing details from equipment manufacturers to allow for termination design by the bus duct manufacturer.
4.5.2Equipment connections will include bolting hardware, bus adapters, insulating materials and assembly drawings.
4.5.3Braided flexible connectors are to be furnished for attachment to porcelain bushings, reactors or generator terminals and will have a continuous current rating equal to or greater than the main conductors.
4.6Insulation
4.6.1600 Volt systems will not require an insulation material applied to the conductors. Adequate air space will be provided between phases and ground so that the system will operate without insulation.
4.6.25kV - 38kV Systems will be insulated using a fluidized bed epoxy process having a continuous rating of 130 degrees C or an approved alternative.
4.6.35kV - 15kV shipping split joints will be insulated with removable boots.
4.6.424kV - 38kV shipping split and factory joints will be insulated described as follows:
4.6.4.1All hardware will be covered with an electrical mastic-filler to fill voids and irregularities.
4.6.4.2A semi-conducting shielding tape will be applied over the entire joint.
4.6.4.3A 130 degree C rated EPR tape will be provided as the primary insulation.
4.6.4.4A PVC jacketing tape will be supplied over the primary insulation.
4.7Grounding
4.7.1A continuous ground system having the same short circuit rating as the main conductors must be provided. The ground can be a separate copper or aluminum bar or an aluminum enclosure.
4.7.2Shipping split ground tie plates require a minimum of four (4) bolts on each side of the connection which use star tooth type washers bolted to unpainted enclosure surfaces.
4.7.3Copper ground pads are to be furnished at equipment connections for attachment to the station grounding systems.
4.8Conductor Support
4.8.1Insulators are to be track resistant, flame retardant and non-hygroscopic, having adequate mechanical strength to withstand forces imposed by the specified short circuit rating.
4.8.2600 Volt systems are to be supported with GPO-3 fiberglass supports.
4.8.35 & 15kV systems will be supported with molded glass polyester or porcelain supports. High alumina ceramic supports are unacceptable. A corona resistant material must be used between the bus insulation and bus supports.
4.9Enclosure
4.9.1High conductivity aluminum enclosures will be used and must be capable of resisting corrosive attack under normal environmental conditions and will be of such design so that no direct water or contaminant path exist into the enclosure.
4.9.2Internal and external surfaces will be finished as described below:
4.9.2.1Surfaces shall be prepared using a high pressure chemical wash and iron phosphate treatment.
4.9.2.2Parts are oven dried prior to application of specified powder coating.
4.9.2.3Powder coating is electrostaticly applied in an environmentally controlled area.
4.9.2.4Coated parts are immediately oven cured in accordance with the manufacture's instructions.
4.9.3Protective plating is required between any mechanical assemblies consisting of unpainted dissimilar metals.
4.9.4Top and bottom covers must be removable for field access to all bus joints, bus supports and heaters.
4.9.5Insulator attachment must be inaccessible with covers in place.
4.9.6All gaskets will be Ethelene Propylene Diene Monomer (EPDM) and will be concealed to prevent deterioration and positioned to prevent assembly hardware from violating the gasket.
4.9.7Screened breather drains are required along bottom covers and at all low points of the installation.
4.9.8Outdoor hardware which is exposed to the elements will be stainless steel an will include seal washers with EPDM gaskets. Indoor hardware will be plated steel.
4.9.9Outdoor top covers will be lipped to prevent entry of wind blown moisture.
4.9.10Indoor ventilated construction will have solid top covers with bottom and side vented per the latest applicable standards.
4.9.11Enclosures are to be shipped in the longest practical shipping lengths (24 foot maximum) to minimize field assembly.
5.0 TESTING
5.1All equipment will be subjected to ANSI-C37.23 standard production tests.
5.2Manufacturer is also required to submit the design tests in accordance with ANSI-C37.23.
Temperature Rise Test
Insulation Withstand Test
Impulse Test
Wet and Dry Withstand Test
Momentary Short Circuit Test
Insulation Flame Test
Weatherproof Test
5.3In addition to the above design tests, all designs will be subjected to a partial discharge test to demonstrate that the insulation system performs corona free at operating voltage and to also determine the corona inception level for each design.
6.0 DRAWINGS
6.1The bus manufacturer will supply specific dimensional drawings for the project which will include the following:
Bus layout and arrangement to include elevation and plan views.
Bus enclosures cross section showing bus conductor and supports. Bus termination details.
6.2Installation and operation manual is included as part of the drawing requirement and will include:
Product description
Receiving and storage
Handling
Installation
Field Testing
Operation
Maintenance
Revised 2/96