Manual 37138C
ESDR 4T - Current Differential Protection Relay
© Woodward
Page 5/46
Chapter 1.
General Information
The ESDR 4T is a three-phase current differential protection relay for generators, motors and transformers in
block connection (protected object). The currents flowing in the individual conductors are each measured using a
current transformer on both sides of the protected object. They form the protection area boundary or zone. All
two or three-phase short-circuits and line-to-earth faults within this protection area are detected by the ESDR 4T
as fault currents which cause tripping. The unit does not trigger if fault currents occur outside the protection
zone. In this way, a selective protection is guaranteed.
All 6 measuring currents are measured in electrical isolation. The unit calculates the differential current and re-
straint current internally for each phase separately. The following settings are taken into account for this:
•
Transformer vector group
•
Rated current of the protection object on the low-voltage side
•
Rated primary current of the current transformer on the high and low-voltage side
•
Voltage transformation of the transformer
The ESDR 4T consists of a basic unit plus various options. The model designation is determined as follows:
ESDR 4T 0 5 -h0018 B/
-ABDEF..Z
Options according to the option list.
These option labels may be found in the operation instructions. The de-
scription of each function will include if it is a standard function or
available only as an option.
Mounting
[B]..Front panel mounting
[M]..Rear wall mounting
Hardware variation
Special types; e.g. other relays
Current transformer, secondary
[1] = ../1 A
[5] = ../5 A
Potential transformer, secondary
[0] = N/A
[1] = 100 Vac
[4] = 400 Vac
Type
Examples:
ESDR 4T01B (standard unit, no voltage measuring and ../1 A CT input, for front panel mounting)