Published on October 26, 2016
1. TESTING OF MOTOR PROTECTION RELAY P225 USING SVERKER750 INJECTION KIT RELAY SETTINGS: Equipment – P012A Phase CTR – 60/5A, Core Balance CT ~ 500/1A, PTR – 6600/100 V Base Current – 50 Amps (Primary) = 50 x 60/5 = 4.2 Amps Relay nominal current In – 5 Amps Thermal overload (49) Setting: I theta (Thermal overload current threshold) = 115 % of I base = 1.15 x 4.2 = 4.8 Amps (Note: Thermal tripping set value in P225 is fixed at 100%. Therefore in order to match the motor setting of 115% overload the I theta set is increased.) Heating Time Constant Te1 = Te2 = 14 minutes. Cooling Time Constant – Tr = 28 minutes. Negative Sequence Current Recognition Factor – Ke = 4 Testing: Connect single phase current injection between two CT’s in series. Disable 46, 48 and 50LR Ensure that the thermal state is reset to zero. Inject 2 x I theta = 9.6 Amps. Thermal Alarm occurs at 90% and trip at 100% thermal state. Note the time to alarm and trip for the cold characteristic. Wait for the thermal state to fall to 90% and inject the same current again Observe the time for tripping and verify with hot curve. Negative Sequence (46) Setting: I2> - 30% In ,Time 6 seconds. Testing: Enable the trip Single phase injection to two CT’s Set the time to zero. Inject 3 x 0.3 x 5 A = 4.5 Amps Observe the pick up value. Increase the time to set value of 6 sec. and inject 1.5 x I pick-up and note the time.
2. Short Circuit (50) Setting: I>> - 8.4 x In, Time – 50 mSec. (To match the setting of 500 Amps. 8.4 x 5 = 42 Amps = 42 x 12 = 504 A (Primary) Testing: Single phase injection to two CT’s Inject 42 Amps and find the pick-up and time delay. Excess Long Start (48) Setting: I start detection = 2.0 I theta, tI start – 6 seconds. Testing: Single phase injection to two CT’s Disable 46 and 50LR Connect 48 V dc supply to relay terminals 22/24 through auxiliary contact of the injection kit to close the contact when injection is started. (To simulate Circuit Breaker contact) Ensure that start detection mode is set to 52 + I. Set the time delay to zero. Increase the injected current to 9.6 Amps to note the pick-up value. Set the time to 6 sec and test the relay function again. Block Rotor (50LR) Setting: I stall detection = 2.0 I theta, tI stall – 6 seconds. Testing: Single phase injection to two CT’s Disable 46 and 48 Set the time delay to zero. Increase the injected current to 9.6 Amps to note the pick-up value. Set the time to 6 sec and test the relay function again. Earth Fault (50G) Setting: I 0 > - 0.006 milli Amps, Time 50 milli Sec. Testing: Connect injection current wires between relay contacts 55 / 56 0 Carry out primary injection and note the current = 2.8 – 3.0 A (Approx.) Carry out secondary injection with a current setting of 1.0 Amp and verify relay operation and time values. RTD Protection (38) Setting: Alarm and Trip settings are made according to the motor make. Testing: Connect resistance box to the RTD terminals at the top of the panel and test by varying the resistance values.