TERM PAPER REPORT (EE382)
On
DISTRIBUTION SYSTEM RELAY
SUBMITTED BY
ANDREW RANI (B19EE008)
B.Tech (Electrical Department)
Faculty in charge
DR. GAYADHAR PANDA
&
SATYAVARTA KUMAR PRINCE
NIT MEGHALAYA
Abstract- Power systems have been facing power quality problems due to the penetration of
harmonics into the transmission systems caused by increasing nonlinear loads.. Several
measurements are performed at different locations in the area, and power quality indices have
been extracted and compared with IEEE 519 Standards. The study shows that the
malfunctioning of the reactor is due to the effect of harmonics on the overvoltage relay
exciting the reactor.
The relation between the harmonic voltage and over voltage behavior is tested in the
laboratory. The effect of harmonics amplitude and phase angle on the relay operation is also
investigated
CONTENT
-INTRODUCTION
-CAUSES OF OVERVOLTAGE
-SYSTEM DESCRIPTION
-MODELLING AND DISCUSSION
-CONCLUSION
INTRODUCTION
A broad Protection relay is a device which controls the operation of a circuit
breaker by means of measuring power system quantities (currents and
voltages) and processing them through its internal logic. The internal logic
allows the relay to initiate a tripping sequence when anomalous conditions
arise within the power system. Protection relays typically consist of one or
more of the following basic protective components: voltage units (i.e. under
voltage and over voltage), over current units, distance protection and
differential protection. Under voltage, over voltage (O.V.) and over current
units are designed to operate when the amplitude of the input quantities
exceeds (or falls below in case of under voltage) a pre-set threshold. The
operation can be instantaneous or time delayed. Harmonics can affect the
operation of sensitive electronic equipment as protective relays. Due to
increase of these distortions, the reliability of protection devices may be
sacrificed. The influence of distorted waveforms on protective relays is not well
documented because of the large variety of measuring principles employed in
different relays.
CAUSES OF OVERVOLTAGE RELAY:
The relay can make incorrect operations such as failure or false tripping. The
reasons of incorrect operation may be personnel error, incorrect settings,
equipment malfunction, poor application or undesired system parameters
(harmonic current and voltage).
Over voltage may also occur due to
 Sudden loss of load
 Improper working of tap changer
 Malfunctioning of Generator AVR
DESCRIPTION:
The figure above is the circuit block I am going to use for the over-voltage relay
process.
MODELLING & DISCUSSION
=>The over voltage setting is usually 110/130% of the normal operating
voltage depending on the system requirement.
=>If the voltage rises than any of the above level for the set amount of time
then the tripping command issued by the relay and hence the system is
isolated
=>if the phase voltage is 230v then the line voltage, vL=√3*230=400v that is
why the input voltage is 400 in the input source
=>And we have choose the over voltage magnitude variation of 0.2 pu
amplitude, then the variation= 230*(0.2) =46v, due to this the total
variation of the over voltage =230+46=276v
=>There at the over voltage relay setting is at 10% then the rated
value=230*0.1=23v this means that the over voltage relay will operate
when the system voltage goes beyond 253v
=>The fig. above is the input voltage from scope.A if we zoom we can clearly
see that we are measuring the peak voltage of phase value =√2*230v=325v
=>And the peak value of the over voltage for 0.2 pu=√2*276v=390.32v
=>The above diagram observed from the scope2 which the over voltage relay
is operated at time =0.3-0.35s
CONCLUSION:
The simulations offer the opportunity for the researcher to create different
energy system models in order to simulate power quality deviations by
connecting different functional blocks into the environment of the simulation.
Therefore, within the simulated model, it provides a perspective on the way
quality deviations propagate and behave.
REFERENCES:
[1] https://in.mathworks.com/matlabcentral/fileexchange/64255-overvoltagerelay-block?s_tid=prof_contriblnk
[2] Overvoltage Relay (ANSI/IEEE C37.2 device number 59)
[3] https://en.wikipedia.org/wiki/Relay