HT EASYTEST - Verify of Protection Coordination L-L, L-N and L-PE

EASYTEST-COMBI519
EN - 109
12.10. VERIFY OF PROTECTION COORDINATION L-L, L-N AND L-PE
Purpose of the test
Testing the coordination of protective devices (typically MCB or fuse) present in a single-
phase or three-phase installation as a function of the limit time of fault extinction by the
protection set by the user and the calculated value of the short-circuit current.
Parts of the system to be checked
The test must be performed at the point in which the minimum short-circuit current is
possible, normally at the end of the line controlled by the protection device in the normal
condition of the line. The test must performed between Phase-Phase in three-phase
installations and between Phase-PE or Phase-PE in single-phase installations.
Allowable values
The instrument performs the comparison between the calculated value of short-circuit
current and the Ia = tripping current of the protection device within the specified time,
according to the following expressions:
aMinLLSC
II 
− 2_
Three-phase system → Loop L-L impedance
aMinNLSC
II 
− _
Single-phase system → Loop L-N impedance
aMinPELSC
II 
− _
Single-phase system → Loop L-PE impedance
where:
Isc L-L_Min2F
=
Prospective short-circuit current minimum double phase L-L
Isc L-N_Min
=
Prospective short-circuit current minimum L-N
Isc L-PE_Min
=
Prospective short-circuit current minimum L-PE
The calculation of prospective short-circuit current is performed by the instrument based
on the fault loop impedance measurement in compliance with the following relationships:
LL
NOM
LL
MI NMinLLSC
Z
U
CI
−
−
−
=
2_
NL
NO M
NL
MI NMinNLSC
Z
U
CI
−
−
−
=
_
PEL
NO M
PEL
MI NMinPESC
Z
U
CI
−
−
−
=
_L
Phase – Phase
Phase – Neutral
Phase – PE
Measured voltage
U
NOM
C
MIN
230V-10% < Vmeasured < 230V+ 10%
230V
0,95
230V+10% < Vmeasured < 400V- 10%
Vmeasured
1,00
400V-10% < Vmeasured < 400V+ 10%
400V
0,95
where:
U L-L
=
Nominal Phase-Phase voltage
U L-N
=
Nominal Phase-Neutral voltage
U L-PE
=
Nominal Phase-PE voltage
Z L-L
=
Measured Phase-Phase Impedance
Z L-N
=
Measured Phase-Neutral Impedance
Z L-PE
=
Measured Phase-PE Impedance