How do you set the operating time of an over current relay?

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 co relays?

The type CO relays consist of an overcurrent unit (CO), an indicating contactor switch (ICS), and an in- dicating instantaneous trip unit (IIT) when required. The principal component parts of the relay and their location are shown in Figures 1 through 5.

What is an ICS relay?

An ICS true off delay relay is an off delay relay that provides a relay contact for a preset delay period after voltage is removed from input terminals A and B. At the completion of the delay cycle, the relay is de-energized and the contact transfer is made.

What type of protection does a co relay typically provide?

TYPICAL APPLICATIONS OF THE CO RELAY 2) Overcurrent protection, phase or ground, where coordination with downstream devices is not involved and 2 to 60 cycle tripping is allowable. CO-5 Long Motor locked rotor protection where allowable locked rotor time is approximately between 10 and 70 seconds.

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%.

What is IDMT over current relay?

Inverse definite minimum time (IDMT) over-current Relay is one in which the operating time is approximately inversely proportional to the fault current near pick-up value and then becomes constant above the pick-up value of the relay.

What is normal inverse curve?

The Normal Inverse portion of the of the curve will be no faster than the Short Time Setting. This is depicted for five of the ST settings as a dashed horizontal lines. The IEC curve has a Pick Up and TimeDial setting. The curve is also dependant on the Short Time setting and will not trip quick than this setting.

What is pick up value of relay?

When a relay operates to open a “b” contact or to close an “a” contact, we say that it “picks up,” and the smallest value of the actuating quantity that will cause such operation, as the quantity is slowly increased from zero, is called the “pickup” value.

How do you calculate overcurrent settings?

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 should be the time setting of relay B?

Assuming a safety margin of 20% to allow for relay errors and a further 10% for variations in the system impedance values, it is reasonable to choose a relay setting of 1.3 x 2200A, that is, 2860A, for the relay at B.

What is protection relay calibration?

5 Days, 8 Hours / Day. Protective relays are decision-making elements in the protection scheme for electrical power systems. They monitor circuit conditions and initiate protective action when an undesired condition is detected.

What is reset value of relay?

When a relay operates to close a “b” contact, or to move to a stop in place of a “b” contact, we say that it “resets”; and the largest value of the actuating quantity at which this occurs, as the quantity is slowly decreased from above the pickup value, is called the “reset” value.

What are the typical time curves of the co-6 and co-7 relay?

Figure 9: Typical Time Curves of the Type CO-6 Relay Sub 2 418246 Type CO Overcurrent Relay 41-101U 11 *Sub 2 418247 Figure 10: Typical Time Curves of the Type CO-7 Relay

How to adjust the operating time of a co-11 relay?

Adjust the permanent magnet keeper until the operating time corresponds to the value of Table 2. For type CO-11 relay only, the 1.30 times tap value operating time from the number 6 time dial position is 53.5 ±5% seconds. It is important that the 1.30 times tap value current be maintained accurately.

What is the overcurrent on a 101U co relay?

41-101U Type CO Overcurrent Relay 18 3% and should return to the backstop at tap value current minus 3%. 6.1.3 Time Curve For type CO-11 relay only, the 1.30 times tap value operating time from the number 6 time dial position is 53.5 ±5% seconds and should be checked first.

What are the time-current curves of a motor protection relay?

Time Current Curves Motor Protection Motor protection relays are typically programmed to operate approximately halfway between Load Current Curve and the Motor Damage Curve. 35 Time Current Curves Motor Protection 36 Time-Current Curves Questions or Comments? Troubleshooting 37 38 Troubleshooting Troubleshooting Tools: