(1) Application
DEP-500 is used for two-winding or three-winding transformers of 110KV or below voltage levels.

(2) Functions
(a) DEP-531 Differential Protection Relay for Transformers
DEP-531 is used as differential protection for transformers of 110KV or below voltage levels. Its main functions are: differential overcurrent time protection, ratio differential protection, blocking when CT wiring broken

(b) DEP-535 Backup Protection for Transformers
DEP-535 is used as backup protection for transformers of 110KV or below voltage levels. It is designed in max. mode, e.g., it can be used for high voltage side, medium voltage side, or low voltage side, the corresponding protection function can be selected by different control word.
Main functions: 3-stage complex-voltage blocked overcurrent protection, 3-stage zero-sequence overcurrent protection, clearance discharging zero-sequence overcurrent protection, zero-sequence overvoltage protection, overvoltage alarming, overload alarming, fan start/stop, tap changer blocking, PT wire broken blocking and alarming, etc.

(c) DEP-539 Non-electrical Protection for Transformers
DEP-539 is used for non-electrical protection of transformers. It has 10 non-electrical restart relays and up to 4 independent operation circuits. It is designed to protect all the non-electrical objects of transformers and the operation circuits in each side of transformers.

(d) DEP-550 communication controller
DEP-550 communication controller is used for manage all the communications among different protection relays. It supervises all the protection relay units, transmits all the messages to master stations or local SCADA system, receives commands from master stations or local SCADA, and exchange data with other intelligent electronic devices.

(3) Specification
(a) Ratings
DC voltage - 220V/110V, ±15%
AC voltage - 100V/57.7V
AC current - 5A/1A
Rated frequency - 50HZ

(b) Setting errors
Current/voltage setting error -<5%
Time setting error -- <1% or 50 ms

(c) Environmental Requirements
Working temperature -- -10 oC ~ +60 oC
Storage temperature -- -30 oC ~ +70 oC
Relative humidity - ≤ 95%
Pressure - 86 ~ 108 kpa

(d) EMC Tests
IEC60255-22-1 HF Disturbance Test with Damped Oscillatory Wave, Class III (2.5KV c.m. 1KV d.m.)
IEC60255-22-2 Electrostatic Discharge Disturbance Tests, Level IV
IEC60255-22-4 Fast Transient Disturbance Tests, Class III

(e) Mechanical Stress Tests, Vibration, Shock Stress and Seismic Vibration
IEC60255-21-1

(f) Overload Resistance
AC current loop: 2 times of rated current, able to continue working without any limit
10 times of rated current, able to continue working for 16 hours
40 times of rated current, able to continue working for 1 hour
AC voltage loop: 1.2 times of rated voltage, able to continue working without any limit

(g) Output contacts
Max. capacity of the output contacts is 150 W/1250w, max. working current is 5 A, but arc extinction is not permitted.

(4) Mechanical data and installation
Standard 4 U chassis, installed in cabinet