ND10 LOW IMPEDANCE RESTRICTED DIFFERENTIAL EARTH FAULT

1. 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 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 CT 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 64 REF 50N 51N 50 51 RELIABLE SOLUTION

7. 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 64 REF 50N 51N 50 51 EASIEST SOLUTION in case of EARTH FAULT DIFFERENTIAL FUNCTION

8. Piazza Federico Mistral, 7 20139 Milano (MI) ITALY Tel: +39.02.5749571 Fax: +39.02.57403763 e-mail: thytronic@thytronic.it company web site: www.thytronic.it products web site: www.pro-n.it External Market Support Oscar Ornago tel. +39.02.57495753 e-mail: o.ornago@thytronic.it