Table 6 Causes and effects on distance protection due to IBRs

Zone impedance (zone 1, zone 2)

21

[32]

IBR

Control system parameters, current limit setting

The relay impedance can be far away from the actual fault impedance

[34]

IBR

Low SC current, reactive current rise time

The initial fault impedance by distance relay moves closer to zone 1 setting even for zone 2 faults

[39]

WF-III

The frequencies of the fault current and voltage can be well apart

Oscillating impedance

[33]

IBR

Phase angles are controlled by inverter control system

The impedance has a great amplitude and phase offset

[40]

Back-to-back Converter

Power electronic converters do not tend to contribute to the fault current

The impedance by relay is very high and it can see outside of the protection zones

[44]

VSC

Design of control system, lower SC-current level

The measured impedance locus has transients. The impedance moves in and out from the effective zone during the fault

[36]

IBR

Low-magnitude currents that may behave incoherently with the voltages

Phase distance element zone 1 may overreach; zone 2 may drop out; oscillating apparent impedance

[37]

IBR

Inverter control system

Effect on impedance, zone 1 overreach

[41]

VSC-HVDC

Reactive power control of VSC-HVDC

Relay tends to overestimate the fault distance

[42, 43]

WF/VSC-HVDC

Different FRT controls, control of current amplitude and phase

Malfunction of the distance relay; the higher line distance relay zone 2 is narrowed

[45]

IBR

Inverter reactive power current

Over reach or under reach of impedance measurement

[46,47,48]

WF-III

Depends on the operating mode

Affects the trip boundaries of the distance relay

Overcurrent starting

50

[35]

IBR

Inverters are nonlinear electronic devices

Insufficient SC-current, delay in operation

Directional element

32P

[38]

WF-III

The short-circuit current mainly consists of a transient component and a steady-state component

Effect on positive-sequence voltage polarized impedance relay

[36]

IBR

Current limited by the inverter

The phase directional element may misbehave when a three-phase fault disconnects the IBR

32Q

[36]

IBR

Negative-sequence current limited

The negative-sequence directional element may misbehave

[49]

WF-III

Low voltage ride requirements

The relationship between the current and voltage phase angle in negative-sequence is not readily known

[50]

IBR, WF-III

Improper magnitude and phase angle of negative-sequence current

The negative-sequence current is not the leading voltage as in a conventional source

[51]

WF-III

Low-voltage ride through requirements

Improper magnitude and phase angle of the negative-sequence current

Fault-type identification and selection

FID

[52]

WF-III

Slip and crowbar resistance

The approximately unequal positive and negative currents will critically affect the phase selectors according to their variation components