What is high set instantaneous overcurrent relay?

The high-set instantaneous setting is typically for protecting a transmission line and is set at a margin below the maximum remote terminal fault magnitude so that it does not over-reach and trip for faults outside the line protection zone.

What causes instantaneous overcurrent?

Possible causes for overcurrent include short circuits, excessive load, incorrect design, an arc fault, or a ground fault. Fuses, circuit breakers, and current limiters are commonly used overcurrent protection (OCP) mechanisms to control the risks.

How do you calculate instantaneous overcurrent?

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 high set overcurrent protection?

MIXED IDMT AND HIGH SET INSTANTANEOUS OVERCURRENT PROTECTION RELAYS. A high-set instantaneous device can be utilized where the source impedance is small in comparison with the protected circuit impedance. This allows a decrease in the operating time at high short circuit levels possible.

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 the difference between overcurrent and overload?

Short circuit is a type of overcurrent. Magnetic circuit breakers, fuses and overcurrent relays are commonly used to provide overcurrent protection. Overload protection is a protection against a running overcurrent that would cause overheating of the protected equipment. Hence, an overload is also type of overcurrent.

Why high set element is provided in harmonic restraint relay?

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.

Which are overcurrent devices?

Overcurrent protection devices include circuit breakers and fuses. Overcurrent protection devices are meant to protect against the potentially dangerous effects of overcurrents, such as an overload current or a short-circuit current, which creates a fault current.

What is TSM and PSM in over current relay?

What is TMS and PMS?

PSM and TMS settings that is Plug Setting Multiplier and Time Multiplier Setting are the settings of a relay used to specify its tripping limits. To understand this concept easily, it is better to know about settings of the Electromechanical Relays.