EQUIPMENT PROTECTION REQUIREMENTS AND OPERATING LIMITATIONS

This section requires the Customer to provide protection that will prevent damage to utilization equipment from normal operations on the Company's supply system. It also provides operating limits for Customer motors and equipment to prevent excessive voltage fluctuations and equipment operating problems.

Equipment covered in this section includes motors, welders, heating equipment, voltage sensitive devices, generators, harmonic producing equipment and other equipment requiring special considerations and protection.

Motors and equipment can have special load requirements that cause excessive voltage and harmonic changes to the Company's system. The Customer shall report any equipment that can cause such changes to the Company's system when applying for service. The Company will evaluate the service requirements and make provisions to minimize problems for the Company or Customer. When the Company must install extra capacity or special equipment to protect against Company system problems caused by the Customer's equipment, the Customer shall pay the excess costs.

REQUIRED EQUIPMENT PROTECTION ON THREE-PHASE SERVICES

The Customer shall install protective devices for all three-phase equipment, and single-phase equipment connected phase-to-phase (especially motors). The devices shall be approved to prevent damage from the loss of a phase, parallel phasing, or reduced voltage. Single-phase motors or equipment connected phase-to-phase can remain energized at a reduced voltage when one of the phases supplying the equipment is lost. The protective devices, usually loss-of-phase relays or under-voltage relays, shall shut down all equipment until they are manually restarted or they shall have at least a two minute time delay before an automatic restart.

Three-phase motors driving elevators, cranes, and similar equipment shall be provided with reverse-phase relays and circuit breakers to disconnect the motor and prevent injury in case of phase reversal.

Motors and their controls, except those approved for automatic starting, shall shut down upon loss of voltage until they are manually restarted. The use of three overcurrent units in motor controls for three-phase motors has been required since the 1971 edition of the National Electrical Code. It is recommended that motor controls installed prior to this requirement be modified to include three over current units.

The Company will not be responsible in any way for damage to Customer's equipment due to the failure of the Customer to provide adequate protective devices, or due to any failures of such devices.

MOTOR-STARTING CURRENT LIMITS

Motors started at rated voltage require inrush currents several times their full-load ratings. The high starting (locked-rotor) currents create voltage dips which may cause objectionable light flicker and problems operating other equipment. The Company has established the following maximum motor-starting current-limits to keep the high currents and voltage dips within industry standards.

(a) Single-Phase 120/240 Volt Services

Motors with locked-rotor currents of 50 amperes or less when operated at 120 volts, or 150 amperes or less at 240 volts may be started at line voltage.

(b) Single-Phase 120/208 Volt Services

Motors with locked-rotor currents of 50 amperes or less when operated at 120 volts, or 150 amperes or less at 208 volts may be started at line voltage.

When 208 volt or 230 volt single-phase motors, 3 horsepower or larger, or motors having locked-rotor currents higher than 100 amperes are installed, the Company shall be notified to make sure the supply facilities are adequate.

(c) Three-Phase 120/208 Volt Services

Three-phase motors with locked-rotor currents less than 160 amperes or rated not higher than 10 horsepower may be started at line voltage.

(d) Three-Phase 230 Volt Services

Three-phase motors with locked-rotor currents less than 220 amperes or rated not higher than 15 horsepower may be started at line voltage.

(e) Motors Larger Than 15 Horsepower

Motors larger than 15 horsepower can be started across the line in many locations depending on the Company's facilities and the Customer's requirements. Contact the Company's Division Office for specific motor starting limits and recommendations. It is important for the Customer to request starting limits as soon as the motor size is chosen so the Company can make the detailed analysis required.

The motor starting current limits are intended to reduce lighting flicker at the service point to a level that is not considered objectionable, however, the lighting flicker may still be visible.

When a motor is started at line voltage, the Company will decide whether to use the rated locked-rotor current calculated from the Code letter, or the actual starting current determined by test. If two or more motors are started simultaneously, the above starting limits shall apply to their combined starting currents. Where a motor is started with a reduced-voltage starter, the motor starting current limits shall not be exceeded during the entire starting period.