What is static overcurrent relay?
What is static overcurrent relay?
Static overcurrent relay is made in the form of a single unit in which diodes, transistors, resistors, capacitors etc., are arranged on printed board and are bolted with epoxy resin.
What is Idmt and DMT relay?
Generally, the over current relays are differentiating with their time of operation. The most commonly used over current relays are IDMT (Inverse definite mean time) over current relays, DT (definite time) over current relays and Instantaneous time over current relays. They are designed to sense the over-current.
What is the function of the O C relay?
Overcurrent Relay Purpose and Ratings. A relay that operates or picks up when it’s current exceeds a predetermined value (setting value) is called Overcurrent Relay. Overcurrent protection protects electrical power systems against excessive currents which are caused by short circuits, ground faults, etc.
How do you set the operating time of an over current relay?
The adjustment of definite-time and inverse-time relays can be carried out by determining two settings: time dial setting and pickup setting. The time dial setting adjusts the time delay before the relay operates whenever the fault current reaches a value equal to, or greater than, the relay current setting.
What are the types of static relay?
Static relays are classified according to the type of the measuring unit or comparator as follows: 1. Electronic Relays 2….Gauss Effect Relays.
- Electronic Relays:
- Transductor (Magnetic Amplifier Relays):
- Rectifier Bridge Relays:
- Transistor Relays:
- Hall Effect Relays:
- Gauss Effect Relays:
What are the advantages of static relay?
Advantages of Static Relay The static relay consumes very less power because of which the burden on the measuring instruments decreases and their accuracy increases. The static relay gives the quick response, long life, high reliability and accuracy and it is shockproof. The reset time of the relay is very less.
What is PSM relay?
Plug setting multiplier (PSM) Indicates the severity of the fault. The plus setting multiplier is used only in electromagnetic relays, not in numerical relays. Therefore, the numerical relay does not require plugs.
What is the relation between current and time in 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 are the different types of overcurrent relay?
An overcurrent relay is a type of protective relay which operates when the load current exceeds a pickup value. It is of two types: instantaneous over current (IOC) relay and definite time overcurrent (DTOC) relay.
What is TSM in relay?
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. It is the ratio of fault current in relay coil to pick-up current.
What are the setting parameters for time delay overcurrent relay?
The current setting of overcurrent relay is generally ranged from 50 % to 200 %, in steps of 25 %. For earth fault relay it is from 10% to 70% in steps of 10%.
How do you protect an overcurrent circuit?
Plug-in fuses are used to protect a circuit board from overcurrent conditions. A glass fuse can be used as a plug-in fuse or in a fuse holder.
What is timetime overcurrent relay?
Time overcurrent relays exhibit different “curves” relating trip time to multiples of pickup current. All 51 relays are inverse in that the amount of time to trip varies inversely with overcurrent magnitude: the greater the sensed current, the less time to trip.
What are the different types of overcurrent relays?
Although there are different types of overcurrent relays but basic working principle of overcurrent relay is more or less same for all. Depending upon time of operation, there are various types of Over Current relays, such as, Instantaneous over current relay. Definite time over current relay.
What is the most difficult type of static relay?
The overcurrent relays, even though simplest of all types of electromechanical relays, are the most difficult static relays. This is because the induction disc characteristics of the overcurrent relays (inverse characteristics) are not amenable to simple mathematical analysis.
How do I determine the time delay setting of an overcurrent?
The process for determining the time delay setting involves: (1) Calculation of a time delay value in definite-time overcurrent elements (2) Selection in inverse-time overcurrent elements of a time- current curve from a family of curves. Note: Instantaneous over current (50) elements have only one setting: the pickup current.
