HT VCB Panel Boards (3.3 KV

HT VCB Panel Boards (3.3 KV – 33 KV)

Definition – HT panel is a metal enclosure fitted with HT Circuit Breakers, relays & metering that is used to receive 3.3KV TO 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. The full form of the 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 Hexafluoride) 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 the 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 systems from faults such as earth faults, overloading & short circuits. Different relays are used to protect from different faults. The function of the relay is to sense the fault & give a tripping command to the circuit breaker of the panel. WTI & OTI relays are used to protect transformers from overheating 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 meters or individual meters.
CT & PT – Current transformers (CT) & Potential transformers (PT) are also important components 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 purposes.

For each component installed in HT panel

R,Y,B Indicating light
Breaker On/Off indicator light
Trip indicator
Spring Charged indicator
Trip circuit healthy indicator
DC fail indicator
OC & EF Relay
Master Trip Relay

Energy Meter
Multifunction Meter
Annunciator Panel
Test, Accept & Reset buttons
Voltage selector switch
T-N-C switch
Emergency switch

Features of HT panel (for 11KV or 33KV)

HT panel receives electrical Supply 11KV or 33KV) from H – pole by 3 core HT cable & then it distributes power through one or more outgoing feeders.
These outgoing feeders are connected with distribution transformers which convert HT supply into 415V, 3-phase 4 wire AC supply.
To measure electrical power consumption, Energy Meter is installed in it,
Meters are installed to measure electrical Voltage, Current, frequency, power factor etc.
240 V ac supply is also used in HT panel for 16A power sockets provided inside panel, for panel lights & space heater.
A space heater is provided in the HT panel to avoid moisture inside the panel.
To measure Incoming Supply voltage, 11KV is converted into 110V through PT (Potential Transformer). And 110V voltmeter is used for voltage measuring purposes.
To measure building load in terms of current, total current of the building is converted into 5A or 1A through CT (Current Transformer). CTs are available in different ranges – 600/5A, 400/5A, 300/5A ….. or 600/1A, 400/1A, 300/1A …