ABB RET670 Commissioning Manual page 206

Section 11
Testing functionality by secondary injection
200
1. Connect the test set for injection of three-phase currents to the appropriate
current terminals of the IED.
2. Go to Main menu/Settings/Setting group n/Current protection/
NegSeqOverCurr2Step/NSOn/General and make sure that the function is
enabled, that is Operation is set to On.
3. Inject current into IEDs in such a way that negative sequence component is
created and then verify that negative sequence component of the injected
currents is calculated correctly by the function. See example below for 1 A
rated current transformer.
4. Inject pure negative sequence current, that is, phase currents with exactly
same magnitude, reversed sequence and exactly 120° phase displaced into the
IED with an initial value below negative sequence current start level. No
output signals should be activated.
Note: If it is difficult to obtain pure negative sequence current for the
secondary injection test, a current corresponding to the two phase short-
circuit condition can be used. A two phase short-circuit gives a negative
sequence current of a magnitude: magnitude = (1/√3) · fault current.
5. Increase the injected current and note the value at which the step 1 of the
function operates. Start signal ST1 must be activated when amplitude of the
negative sequence current lies slightly above the start level I2-1>.
Corresponding trip signals TR1 and TRIP is activated after the pre-set time
delay has expired.
Note: Block or disable operation of step 2 when testing step 1 if the injected
current activates the step 2.
6. Decrease the current slowly and note the reset value.
7. Connect a trip output contact to a timer.
8. Set the current to 200% of the start level of the step 1, switch on the current
and check the definite time delay for trip signals TR1 and TRIP. Once the
measured negative sequence current exceeds the set start level I2-1>, the
settable definite timer t1 starts to count and trip signals is released after the
set time delay has elapsed. The same test must be carried out to check the
accuracy of definite time delay for ALARM signal.
Note: The output ALARM is operated by START signal.
9. If inverse time is selected the trip signals TR1 and TRIP operates after a time
corresponding to the formula:
This means that if current jumps from 0 to 2 times start and negative
sequence capability value of generator K1 is set to 10 s and current start level
1


2
I 2 1
− >
 

 
100
 

[ ]
t s
=
2

( )
Multiple of Start



Transformer protection RET670 2.2 IEC
1MRK 504 165-UEN A




K K
⋅




Commissioning manual