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Cable Testing : Circuit Breakers : Co-ordination Studies : Low Voltage : Maintenance :
MV Switchgear : MV Testing : Substation Structure : Transformers

Substation Structure

Substation structure is a very popular solution in design of high voltage substations. The structure consists of metal L profiles connected with bolted or welded connections.

A regular maintenance of the high voltage structure should include checking for physical damage, mechanical stability and electrical clearances and cleaning and testing the structure electrical components. Cleaning and testing should be performed on the:

  • high voltage station insulators
  • lightning arresters
  • high voltage fuses
  • disconnecting switches

Also, substation fence and electrical grounding should be checked and tested on regular basis as part of a regular maintenance program.

Inspection of MV Station Structure


Lightning (Surge) Arresters
The distribution system can be subject to voltage transients caused by lighting or switching surges. To protect power system equipment from these high voltage surges is task of the lightning (surge) arrester. Under normal conditions a surge arrester is an insulator. When a transient voltage is high enough to damage other equipment a surge arrester becomes a low impedance path from phase wire to ground discharging the transient surge current. After discharging the surge current the arrester again becomes an insulator. Under normal conditions, maintenance of a surge arrester consists of cleaning, checking porcelain casing for physical damage and a megoometer testing.

High Voltage Fuses
Fuses are overcurrent protective devices containing a calibrated current-carrying member which melts and opens under specified overcurrent conditions. To perform this function fuses should be regularly inspected during maintenance program. A regular maintenance consists of cleaning of the fuse housing and electrical contacts, checking for physical damage and megohmmeter and ductor testing.


Substation Surge Arresters and HV Fuses


Disconnecting Switch
Disconnecting switch is a switch which is intended to open a circuit only after the load has been removed by some other means. Theyare used primarily for isolation of equipment such as buses or other live apparatus. They are used for sectionalizing electric circuits such as buses or lated circuits or even portions of main feeders for special purposes such as testing and maintenance. The station type of disconnect switch is equipped with a operating shaft mechanism which connects all phases of the switch together and ensures simultaneous opening of all phases.. A regular maintenance consists of checking for physical damage, electrical contacts cleaning and exercising and lubricating the operating shaft mechanism.

Grounding
Good electrical grounding helps protect equipment, personnel and electric power quality. Grounds can shield people, equipment and structures from lightning strikes and fault conditions. Grounded surge arresters protect equipment against transient over-voltages. Grounds help provide fast, reliable protective relaying by making it possible to detect ground current flow upon a ground fault and to quickly actuate a protective relay. Grounding provides a reference potential in system analysis. Grounding serves the needs of fire prevention, electrical safety and loss control including fault and lightning damage control. For these reasons, we verify the ground system, where possible, for the cycle of the program. As part of the full maintenance program, ground resistance is measured using the 3 terminal fall of potential test method.

Fence
Due to the inherent hazards within a substation, a note of the general condition of the station enclosures should be made to ensure safe distances are maintained and dangers are identified.


Substation Compaund

 

Cable Testing : Circuit Breakers : Co-ordination Studies : Low Voltage : Maintenance :
MV Switchgear : MV Testing : Substation Structure : Transformers