Directional relay opeartes +/- 90degree of MTA (maxumum torque angle). Relay is set either forward or reverse depending on the direction of current flow. 180 degree to MTA is always restraint region. Some relay has chareteristic of +/- 85 degree to MTA.
Directional relay is that relay which operate in the direction of the fault current. SAPTARSHI BHOWMICK
Using a test set. The manual gives step by step procedures for this.
A Fuse or a circuit breaker can be used to protect an electric circuit from over loads. A surge arrestor / over voltage relay can be provided for voltage protection An ELCB/ Earth fault Relay may be provided for earth fault protection. Electrix Chennai, India.
an warm air mass takes on the characteristics of the region over witch it forms.
It is something where a fungi is produce as an animal that can reproduce over and over again.
beacuse reaction over controal
crossing over
The synchronous generator when act as a motor that relay is operated. or reverse power relay is acted. mainly it sence thet direction of power flow direction
earth fault relay is also a type of over current relay but the set value of current or relay sensing current is much less than the maximum load current.in over current relay relay sensing current ise than maximum load current mor
over current protection relay
current relay are using for over current low state & high state.but potential relay are related to voltage.
An over current relay will operate when current exceeds its design rating. This application is intended protect loads or circuits from excessive current.
in electrical circuit current will increase specific level (full load current).its call over current
The directional part. Directional relays will operate for events "in front of" them, but will not operate for events "behind" them. Typically directional relays are used in non radial situations such as on the bulk electric system. Non-directional overcurrents are commonly used on radial lines.
ocr-over current relay(senses the over current in the circuits) efr-earth fault relay uvr-under voltage relay
Time delay protective relays used in the power industry can be time over current or voltage, or definite time over / under voltage / over current.Definite time type relays use an over / under voltage / current element that picks up when voltage / current reach a specified level. When this picks up, a timer is started. If current / voltage stays above / below the pickup value for long enough to allow the timer to expire, the relay trip contacts are closed.Time over current elements use an inverse time - current curve to define speed of operation, so the more current is present, the faster the relay will operate.
Instantaneous over current relay, which operates very fast with no intentional time delay and the operating time of these relay can be as low as 0.01sec . These relay operates only when the impedance between the relay and the source zsis very small compared to the impedance to the impedance of the protected section zl .
Over Current (Inverse Time) Over current relay function monitors the general balanced overloading and has current/time settings. This is determined by the overall protective discrimination scheme. There advantage over definite time relays is that they can have much shorter tripping times can be obtained without any risk to the protection selection process. These are classified in accordance with there characteristic curves, this indicates the speed of the operation. Based on this they are defined as being inverse, very inverse or extremely inverse. The typical settings for these relays are 0.7-2In (normal or rated generator current) in 1-10 second. Inducing a calibrated test current through the normal load current tests this relay.
A definite time over-current relay operates like an instantaneous over-current relay coupled with a timer. Once current reaches the pick-up value, it initiates the timing circuit. As long as current stays above this pick-up value, the timer will continue to time. Once the definite time setting is reached, the relay gives trip signal to the circuit breaker.