The BLOCK signal is a general purpose blocking signal of the pole discordance
protection. It can be connected to a binary input in the IED in order to receive a block
command from external devices or can be software connected to other internal
functions in the IED itself in order to receive a block command from internal
functions. Through OR gate it can be connected to both binary inputs and internal
function outputs.
If the pole discordance protection is enabled, then two different criteria can generate
a trip signal TRIP:
• Pole discordance signaling from the circuit breaker.
• Unsymmetrical current detection.
6.9.7.1 Pole discordance signaling from circuit breaker
If one or two poles of the circuit breaker have failed to open or to close (pole
discordance status), then the function input EXTPDIND is activated from the pole
discordance signal in figure
60. After a settable time tTrip, a 150 ms trip pulse
command TRIP is generated by the pole discordance function.
6.9.7.2 Unsymmetrical current detection
Unsymmetrical current indicated if:
• any phase current is lower than CurrUnsymLevel of the highest current in the
three phases.
• the highest phase current is greater than CurrRelLevel of IBase.
If these conditions are true, an unsymmetrical condition is detected. This detection is
enabled to generate a trip after a set time delay tTrip if the detection occurs in the next
200 ms after the circuit breaker has received a command to open trip or close and if the
unbalance persists. The 200 ms limitation is for avoiding unwanted operation during
unsymmetrical load conditions.
The pole discordance protection is informed that a trip or close command has been
given to the circuit breaker through the inputs CLOSECMD (for closing command
information) and OPENCMD (for opening command information). These inputs can
be connected to terminal binary inputs if the information are generated from the field
(that is from auxiliary contacts of the close and open push buttons) or may be software
connected to the outputs of other integrated functions (that is close command from a
control function or a general trip from integrated protections).
Section 6 1MRK 511 287-UEN A
Current protection
140
Technical manual
To Next Page
Loading...
Need help?
General
