ABB RET670 - Page 216

• VA: Ampl = 105/ √3; Angle = 0°
• VB: Ampl = 105/ √3; Angle = 240°
• VC: Ampl = 105 / √3; Angle = 120°
4. Inject the voltages that are related to the first part of the characteristic, and then
slowly increase the phase current IA from 0.0 A up to the value the function trips.
The PICKUP and STOC signals must be activated when the amplitude of the phase
current IA is slightly above 0.25 A on the secondary side. The corresponding trip
signals TROC and TRIP will be activated after the pre-set time delay has expired.
5. Decrease the current IA slowly and note the reset value.
6. Repeat steps 4 and 5 applying voltages that are related to the second and the last
section of the characteristic; the function trips when IA is slightly higher than: 0.5 A
in the second section; 5A in the last section.
7. Connect the trip output contact to the input channel of the test set in order to stop the
injection and measure the trip time.
8. If definite time delay is used for the overcurrent step, set the setting Characterist =
ANSI Def. Time. Apply the voltages related to the last part of the characteristic and
inject a current IA 200% higher than the set tripping level, and check the definite
time delay for trip (the signals TROC and TRIP of the protection function VRPVOC
are active in trip condition).
9. If inverse time delay is used for the overcurrent step, the parameter setting
Characterist shall be properly set; we can refer, for example, to the setting IEC Very
inv.; If the IEC Very inverse time characteristic is selected, the trip signals TROC
and TRIP will trip after a time defined by the equation:
t s
k
I
Pickup Curr
[ ]
=






−
13 5
1
. *
_
ANSIEQUATION2435 V1 EN (Equation 94)
where:
t Trip time in seconds
I Measured value (for example, phase current)
Pickup_Curr Set trip value
This means that if the measured phase current jumps from 0 to 2 times the set trip
level and time multiplier k is set to 1.0 s (default value), then the TROC and TRIP
signals will trip after a time delay equal to 13.5 s ± tolerance.
Taking into account the above explanation, inject the voltages related to the last part
of the characteristic and inject a current IA 200% higher than the set operation level,
and check the trip time delay.
Section 11 1MRK 504 165-UUS -
Testing functionality by secondary injection
210 Transformer protection RET670 2.2 ANSI
Commissioning manual