KD Relay
Application:
• Compensator distance
relay that provides a
single zone of phase
protection for all three
phases.
• It provides tripping for
phase to phase, two phase
to ground and three phase
faults within the reach
setting and sensitivity
level of the relay
KD Relay Construction
Cylinder Unit:
• Main function is to
operate when the angle
between two signal
applied is within
certain range.
• Widely used as a
directional unit and in
impedance relays.
KD Relay Construction
Cylinder Unit:
• T=KI1I2SIN(Ø12-Ø)-KS
• Where K and Ø are
design constants.
• Different combinations
of input quantities can be
used for different
applications, system
voltages or currents or
network voltages.
KD Relay Construction
Compensator:
• Designated as T
• Current to Voltage air
gap transformer.
• Voltage side has a tap
which divides the
winding in two sections.
• The output voltage angle
can be changed by
connecting a resistor
across one of the voltage
winding sections
KD Relay Construction
Compensator:
KD Relay
KD Relay
Operation:
KD Relay
KD Relay
C3C Capacitor
KD Relay
Impedance Circle
KD Relay
Impedance Curve
KD Relay
KD RELAY
Equations needed for testing
Z Setting 
ST
1 M
Relay Setting
•Impedance measured by 3 phase unit
Zr 
VLL
3  IL
IL 
VLL
3 Z Setting
Used to find required test current
•Impedance measured by 2 phase unit
Zr 
VLL
2 IL
IL 
VLL
2  Z Setting
Used to find required test current
Tests Required
• Main tests required are the compensator
check, maximum torque angle and the
impedance test for 3 phase unit and phase to
phase units.