This is an arrangement of electrical conductors, towers, protective equipment, transformers etc for the operation and maintenance of a power transmission network.
Most common equipments found in a GSS with few abbreviations are:
- Power transformers
- Circuit Breakers (CB)
- Isolators
- Current transformers (CT)
- Potential transformers (PT)/ Capacitive voltage transformers (CVT)
- Bus bars (BB)
- Surge arrestors (SA)
- Line trap (for PLC communication)
- Earthing transformers
- Auto-Recloser
- Overhead earth wire
- Underground earthing system
Power transformers:
When classified depending on the voltage levels in both sides of a transformer:
- step-up type (used in voltage increase from alternator-> transmission line)
- step-down type (used in voltage decrease from transmission line->distribution)
Classified depending on the insulation medium:
- mineral oil-filled type
- dry-type
Circuit Breakers :
These are normally classified according to the arc-quenching medium around the contacts:
- Air circuit breakers; Air Blast circuit breakers (ACB)
- Vacuum circuit breakers (VCB)
- Oil circuit breakers (OCB)
- Gas circuit breakers (eg: SF6 breakers)
Isolators:
These are mechanical devices used to open an electrical path. This is particularly vital as a visual indication of isolating high voltage components, which is not provided by a CB.
These can be operated only in Off-Load condition
Current transformers:
A type of transformer used to reduce the magnitude of the flowing current in a conductor, so that current can be handled safely for measurement & instrumentation.
Primary side is the current measured and secondary side will have the reduced current. Reduction in magnitude will be determined by the turns ratio (e.g.: 400/5, 1000/5, 2000/5 etc. ).
Always secondary side of a CT is NEVER open-circuited. This is to avoid the dangerous high voltage present in the secondary side of the CT.
Potential transformers:
A type of transformer used to reduce the magnitude of the voltage in a conductor, so that voltage can be handled safely for measurement & instrumentation.
Like CTs, reduction in voltage will be determined by the turns ratio of a PT.
Busbars:
These are normally made of hollow Copper/Aluminum rods. The reason is to account for the high current flow so that normal cables would be unable to withstand the electrical stress produced.
Surge arrestors/ Lightning arrestor:
These are devices made for the protection of a power system arising from dangerous surges. These surges (high voltage impulses of shorter duration) are either from lightning or load switching.