No work shall be performed on incoming power supplies (for example, electrical service entrance lines from utilities, or customer feeds) without prior notification and approval from the field representative Electrical Engineering department representative. Its very important to discuss on Working on Incoming Power System.
Working on Incoming Power System (during construction)
Location of Safety Grounds
- —Safety grounds shall be installed where the incoming power supply is connected to the facility distribution equipment (for example, substation circuit breaker, substation transformer, switchgear, or main service disconnecting means) as soon as the distribution equipment is set in place. Safety grounds can be removed for connection of the incoming power lines to the equipment; however, they shall be reconnected as soon as the installation of the incoming power lines has been completed. Safety grounds must remain connected until the power system is ready to be energized. All safety ground connection locations must be identified on the facility Safety Work Permit form and shall be tagged per requirements of the lock-out tag-out process.
- For substations at new site locations or new substation additions to existing facilities, the responsible Air Products representative will maintain communication with the incoming power supplier throughout the construction of the substation to ensure that there is always control over the energization process. The Air Products representative will schedule the time for the connection and energization of the incoming power. Every effort will be made to schedule the connection of the supplier’s incoming power lines just before energization of the substation to avoid possible energization before substation work has been completed.
- The representative will establish and maintain communications with the respective customer’s representative to ensure that there is always control over the energization process.
Safety Work Permit System for Safety Grounds
- Preference is to have a visible line break, rather than an open switch, until it is time to energize the substation. After the incoming power cables have been terminated, all activities within the substation, including isolation of the incoming power lines, shall be controlled by the Safety Work Permit system. This precaution is required to protect workers in the substation from exposure to hazardous energy caused by inadvertent energization of the substation. Whenever work in the substation is necessary within 5 m (15 ft) radius to energized power conductors under 200KV and 6 m (20 ft) >201KV to 350KV and 8 m (25 ft) for 351KV to 500KV, or if work is to be performed on any energized line, the power to the substation shall be disconnected by having the power supplier disconnect the incoming power to the facility outside of the substation and lock and tag all the switches within the substation in the open position.
- In addition to the requirements identified in paragraph 5.8.4, safety grounds shall be installed on all incoming power lines. These safety grounds shall be installed as soon as the incoming power lines are installed. Whenever possible, safety grounds shall be installed on the incoming power lines in such a manner that they do not require removal for performing work during construction. Safety grounds must remain connected until the power system is ready to be energized. (Refer to Removal of Safety Grounds)
- The electrical contract for substation erection shall be reviewed by the Department to ensure that the contract specifies installation of grounding straps at the proper locations in the substation, and that the straps will be installed before any incoming power line to the substation is connected. The erecting contractor shall install safety grounding straps of the appropriate capacity: (1) at the substation structure or (2) before the first set of switches or (3) at the specific piece of equipment being worked on. The erecting contractor shall install grounding straps even if there are safety grounds or safety ground switches in the incoming lines to the substation.
Method of Attachment
—The exact method for attachment of the safety grounds shall be reviewed with the field representative. Safety ground can be installed either across all phase legs then to ground or individually from each phase leg to ground. Safety grounds shall preferably be attached to the nearest available grounding electrode system conductor. The entire safety ground connection from incoming power line to ground connection shall be visible from a single location.
The contractor shall be responsible for providing all required safety grounding cables. The size of safety grounding conductors shall be based on the available fault current rating of the incoming power supply; however, conductors shall not be smaller than #2/0 AWG stranded copper. Connection clamps shall be provided to match the equipment to which the safety grounds are being connected. It shall be the responsibility of the contractor to ensure that safety grounding cables are properly tested and maintained in first class working order. Safety grounding cables displaying any signs of damage shall not be installed.
Communication with Power Supplier
Whenever the incoming power supplier must temporarily de-energize the system, the representative shall maintain communication with the power supplier’s representatives and shall notify the power supplier when it is safe to restore power to the facility.
All personnel involved in the construction of the incoming power system shall be made aware that there is always a potential for back feeds from the low voltage system to the high voltage system if transformers are connected and power is inadvertently applied to the low side of a transformer.
Removal of Safety Grounds
After completion of facility construction and before the initial energization of the incoming power supply, all safety grounds shall be removed and the location of each safety ground shall be inspected by the field representative, an Air Products Global Support Services (GSS) Electrical Engineering Department representative, or both depending on availability at the site, to ensure safety grounds have been removed.
After ensuring that all safety grounds have been removed, the field representative shall notify the incoming power supplier that it is safe to energize the system for the first time. The responsibility for performing this notification shall be mutually determined by the field representative before final inspection of the safety ground removal.