General description

The EBR-3000 relay, combined with an EBR-Z (EBR-3Z), is a digital

protection relay designed for high impedance differential protection

schemes . The intuitive operating system with validation checks and

extensive commissioning functions such as the built-in fault simula

tor allow safe and time-optimized maintenance and commissioning .

The parameter setting and evaluation software PowerPort-E can be

used consistently across the entire family of E-Series relays .

The principle of the high impedance differential protection is compa

rable with low impedance differential protection: Calculate and moni

tor the sum of all the currents flowing into the protected object, and

under non-fault conditions the sum is zero . Any differential current,

however, is forced through the high impedance of the high imped

ance relay .

The input of the high impedance relay consists of a resistance

(EBR-Z) and an overcurrent protection element (ANSI 87 in the EBR

3000) .

The following convention is important to know: Even though the

EBR-3000 measures the currents flowing through the stabilizing

resistor, all the measurements are presented as a voltage across

this stabilizing resistor (which is 2000 Ω for the EBR-Z) . The burden

of the EBR-3000 measuring input (which is in series with the EBR-Z

resistor) can be neglected compared to the 2000 Ω impedance .

The EBR-3000 monitors the magnitude of this voltage to differenti

ate between in-zone and through faults .

A varistor is built into the EBR-Z . It is connected across the input of

the relay to avoid damage to the relay caused by high voltage . The

varistor needs to be able to conduct significant power as the paral

leled CTs deliver current under special fault circumstances (e . g . in

case of a breaker failure) for more than 30 cycles .

To prevent damage to the relay due to system issues, a lockout relay

is required to short-circuit the high impedance when an trip is initi

ated .