HT panel is a metal enclosure fitted with HT Circuit Breakers, relays & metering that is used to receive 11KV/33KV supply (from one or more source) & distribute the power through its outgoing feeders. Outgoing feeder may be one or more it depends on the load of the building.
Full form of HT panel is High Tension Panel. It is installed in Electrical substations of Commercial complexes, residential colonies, factories, schools, hospitals etc. to receive & distribute HT supply.
Main functions of HT panel –
- To make & break HT supply (or switch on or switch off supply),
- To receive & distribute HT supply,
- To provide protection against faults such as short circuit, overload, earth fault, overheating of transformers winding, overheating of transformer oil.
- To provide metering to monitor various parameters.
Main components of HT Panel – HT panel consists of following components –
- Circuit breakers – these circuit breakers are used for switching ON / OFF HT supply (11KV or 33KV). The switching On/OFF may be done manually, automatic through relays, locally or remotely. Different – different circuit breakers are available such as Vacuum Circuit Breaker (VCB), SF6 (Sulphur Hexa Fluoride) Circuit Breaker & Oil type circuit breakers, but VCB is mostly used in HT panels. A HT panel may have one or more circuit breakers depending on the requirement of electrical distribution system. The circuit breaker may be operated mechanically (through a push button) and electrically (through a switch).
- Relays – Different relays may be used in a HT panel to protect electrical system from fault such as earth fault, overlading & short circuits. Different relays are used to protect from different faults. The function of relay is to sense the fault & give tripping command to circuit breaker of the panel. WTI & OTI relays are used to protect transformers from over heating of winding & Oil.
- Meters – Different meters may be installed on HT panel to measure/record various parameters such as incoming voltage, current, power factor, energy consumption, Load in Kw etc. These parameters may be measured through multifunction meter or individual meters.
- CT & PT – Current transformers (CT) & Potential transformers (PT) are also important component of HT panel. The function of CT & PT is to reduce the actual value of current & voltage respectively to a very low value so that low values could be used for metering & protection purpose.
For example, 200A ampere current can be reduced to 5A or 1A. Similarly, 11KV voltage can be reduced to 110V.
