## Which relay is used for the protection of transformer?

The protection of a transformer against the overloads is performed by a dedicated protection usually called thermal overload relay. This type of protection simulates the temperature of the transformer’s windings.

## How many relays does a transformer have?

Relays for Transformer Protection

SL Voltage Ratio and Capacity of Transformer Common Relays
9 400/220KV 315MVA Differential Relay Overflux Relay Buchholz Relay OLTC Buchholz Relay PRV Relay OT Trip Relay WT Trip Relay Over Load (Alarm) Relay

## Which relay can protect a transformer from heavy fire?

1. Buchholz (Gas) Relay. The Buchholz protection is a mechanical fault detector for electrical faults in oil-immersed transformers. The Buchholz (gas) relay is placed in the piping between the transformer main tank and the oil conservator.

## Why a high set instantaneous OC relay is used in transformer protection and how is it set?

A high-set instantaneous relay element is often provided, the current setting being chosen to avoid operation for a secondary short circuit. This enables high-speed clearance of primary terminal short circuits.

## What is the function of relay in power transformer?

The Buchholz relay purpose is to give the protection to a transformer from the different faults happening in the transformer like the Short circuit, inter-turn, core, incipient, etc. This relay will sense these faults and shuts the alarm circuit.

## How do you protect the secondary side of a transformer?

Overcurrent protection is not required on the secondary side of the transformer to protect the secondary conductors, but overcurrent protection is required for branch-circuit panelboards. This OCPD must be on the secondary side of the transformer, and typically it’s within the panelboard.

## Which relay provide signal before the fault?

Therefore a Bucholz relay provides a signal in case of incipient fault and is a relay that provides a signal before the occurrence of a serious fault.

## How do you set up a relay?

Calculation of Over Current Relay Setting:

1. Over Load Current (In) = Feeder Load Current X Relay setting = 384 X 125% =480 Amp.
2. Required Over Load Relay Plug Setting= Over Load Current (In) / CT Primary Current.
3. Required Over Load Relay Plug Setting = 480 / 600 = 0.8.

## What is PSM and TSM?

Time Setting Multiplier (TSM): The arrangement provided for setting the operating time of protective relay from zero sec to maximum permissible time for a specified current setting is known as time setting multiplier. Plug Setting Multiplier (PSM): It is the ratio of fault current in relay coil to pick-up current.

## What is a 50 51 relay?

50/51 and 50/51N relays. Overcurrent relays are the most commonly-used protective relay type. Time-overcurrent relays are available with various timing characteristics to coordinate with other protective devices and to protect specific equipment.

## What is TMS relay?

Time Multiplier Setting used to change the value of operation of the relay. If it is more the relay will take more time to operate and vice versa. Changing the position of TMS setting, changes the distance between the contact of the rotating disk and the coil.

## What is Idmt relay?

IDMT relay is inverse definite minimum time relay. It is one in which Time of operation is inversely proportional to magnitude of fault current near pickup value and becomes substantially constant slightly above the pickup value of the Relay.

## What is operating time of relay?

The operating time is the time from when the rated voltage is applied to the coil, until the time when the contacts operate. With Relays that have multiple pairs of contacts, if there are no other conditions, then the operating time is the time required for the slowest pair of contacts to operate.

## What is CDG relay?

Type CDG 11. Overcurrent and Earthfault Relay. General description. A non-directional heavily damped induction disc relay which has an adjustable inverse time/current characteristic with a definite minimum time. The relay has a high torque movement combined with low burden and low overshoot.

## What is a MHO relay?

Mho relay is a voltage restrained directional relay. Important Points: Reactance relay is suitable for the protection of a short transmission line because its operation is independent of arc resistance. The relay which is selected for a long transmission line should be less affected due to power swings.

## Where is mho relay used?

Mho distance relays are widely used for the protection of uncompensated and series compensated transmission lines in order to determine the presence and location of faults.

## What is Burden relay?

Burden in current transformer terminology is the load connected to the secondary terminals and is expressed either as VA (volt-ampere) and power factor at a specified value of current, or as total ohms impedance with the effective resistance and reactive components.