Specifications

PIP ELCGL01
November 2002 Electrical Design Criteria
Process Industry Practices Page 13 of 20
7.4.5 Where medium-voltage adjustable speed drives are required, they shall be
specified as in PIP ELSMC21 unless specified otherwise on the Data Sheet.
7.4.6 A microprocessor-based motor protective relay of the type specified on the
Data Sheet shall be provided for motor and motor circuit protection.
7.4.7 Differential protection shall be provided for medium-voltage motors
≥1500 hp unless specified otherwise on the Data Sheet.
8. Grounding
8.1 Substation
A ground grid or loop shall be provided and shall be designed in accordance with
IEEE 80 and the NEC. Grid conductors shall be bare or covered stranded copper as
specified on the Data Sheet and sized to accommodate the worst case fault
condition. If a substation fence is provided, the grid shall include a perimeter loop
located 3 feet outside the fence and bonded to the fence and gates.
8.2 System Grounding
8.2.1 Electrical systems shall be grounded and bonded in accordance with
Article 250 of the NEC. System grounding shall be as specified on the Data
Sheet (see Section 3.5 of this Practice).
8.2.2 480-volt systems shall be wye-connected, high-resistance grounded using
equipment specified in PIP ELSGS01 unless specified otherwise on the Data
Sheet. Alarms from high-resistance grounding systems shall be connected to
plant monitoring system.
8.2.3 Medium-voltage motor control buses shall be low-resistance grounded using
transformer neutral grounding resistors as specified in PIP ELSGS11 unless
specified otherwise on the Data Sheet.
8.2.4 Medium-voltage distribution systems that are derived from owner-supplied
transformers shall be low-resistance grounded using transformer neutral
grounding resistors as specified in PIP ELSGS11 unless specified otherwise
on the Data Sheet.
8.3 Equipment Grounding
8.3.1 The path to ground from circuits, equipment, and enclosures shall be
permanent and continuous; shall have ample capacity to conduct any ground
fault current likely to be imposed on it; and shall be of low impedance. The
equipment-grounding conductors shall be of the types permitted in
Article 250 of the NEC and as specified on the Data Sheet. They shall be
connected to the grounding electrode at the service-supplied or separately
derived system. Ground fault current path continuity must be maintained in
circuits passing through non-metallic enclosures or raceways.
8.3.2 When specified on the Data Sheet or for motors rated 2300 volts and higher,
motors shall also be bonded to one of the following: