1. LOW IMPEDANCE RESTRICTED DIFFERENTIAL EARTH FAULT
ND10
LOW IMPEDANCE RESTRICTED DIFFERENTIAL EARTH FAULT

2. PROTECTIVE FUNCTIONS 50/51 Phase overcurrent
50N/51N - 87NHIZ. Residual overcurrent or high impedance restricted differential ground fault
64REF Biased restricted differential ground fault
BF Breaker Failure

3. 64REF – MOST COMMON APPLICATIONS
Like every differential protective function 64REF is largely adopted in case of high selectivity needs.
Common applications are generator protection and transformer protection. G ~
64REF
64REF

4. BEFORE ND10 – 87NHIZ ONLY SEVERAL CONS Design Large cubicle NAXX
STABILIZING RESISTOR
SEVERAL CONS
Design
Large cubicle
Connections
Low liability
External devices
NAXX
3 CT’s
Low leakage reactance type according to IEC Class PX, TPS or BS Class X
87N
METROSIL
50 51
3 CT’s
Phase Currents
EXPENSIVE SOLUTION

5. ND10 – ONE DEVICE ONLY ND10 CHEAPER SOLUTION CT 3 CT’s
Residual current
ND10
50 51
3 CT’s
Phase Currents
CHEAPER SOLUTION

6. ND10 – 64 REF LOW IMPEDANCE FROM SAME INPUTS
Separate inputs for phase current and current from earth connection.
Earth overcurrent and biased restricted earth fault protective functions both contemporaneously performed.
Phase overcurrent protective function from same 3 CT’s set.
ND10
50N 51N
64 REF
50 51
RELIABLE SOLUTION

7. EASIEST SOLUTION in case of EARTH FAULT DIFFERENTIAL FUNCTION
ND10 – MANY ADVANTAGES
Biased 64REF is internally calculated.
Easy connections.
RS and METROSIL design is not required.
No one external device is needed for stabilization.
Smaller cubicles.
ND10
50N 51N
64 REF
50 51
EASIEST SOLUTION in case of EARTH FAULT DIFFERENTIAL FUNCTION

8. External Market Support Oscar Ornago tel. +39.02.57495753
Piazza Federico Mistral, 7
20139 Milano (MI)
ITALY
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External Market Support
Oscar Ornago
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