Built-In Overcurrent Protection Steps - ABB Relion 670 Series RES670 Technical Manual

1MRK 511 365-UUS A
11.1.6.3
Phasor measurement unit RES670 2.1 ANSI
Technical manual
Base current shall be entered as:
1. rated phase current of the protected object in primary amperes, when the measured
Current Quantity is selected from 1 to 9, as shown in table 191.
2. rated phase current of the protected object in primary amperes multiplied by √3
(1.732*Iphase), when the measured Current Quantity is selected from 10 to 15, as
shown in table 191.
Base voltage shall be entered as:
1. rated phase-to-ground voltage of the protected object in primary kV, when the
measured Voltage Quantity is selected from 1 to 9, as shown in table 192.
2. rated phase-to-phase voltage of the protected object in primary kV, when the
measured Voltage Quantity is selected from 10 to 15, as shown in table 192.

Built-in overcurrent protection steps

Two overcurrent protection steps are available. They are absolutely identical and
therefore only one will be explained here.
Overcurrent step simply compares the magnitude of the measured current quantity (see
table 191) with the set pickup level. Non-directional overcurrent step will pickup if the
magnitude of the measured current quantity is bigger than this set level. However
depending on other enabled built-in features this overcurrent pickup might not cause the
overcurrent step pickup signal. Pickup signal will only come if all of the enabled built-in
features in the overcurrent step are fulfilled at the same time.
Second harmonic feature
The overcurrent protection step can be restrained by a second harmonic component in the
measured current quantity (see table 191). However it shall be noted that this feature is not
applicable when one of the following measured currents is selected:
• PosSeq (positive sequence current)
• NegSeq (negative sequence current)
• UnbalancePh (unbalance phase current)
• UnbalancePh-Ph (unbalance ph-ph current)
This feature will simple prevent overcurrent step pickup if the second-to-first harmonic
ratio in the measured current exceeds the set level.
Directional feature
The overcurrent protection step operation can be made dependent on the relevant phase
angle between measured current phasor (see table 191) and measured voltage phasor (see
table 192). In protection terminology it means that the General currrent and voltage
Section 11
Multipurpose protection
335