Switch Gear and Protection · Power System Analysis · GATE EE

Marks 1

For the three-bus power system shown in the figure, the trip signals to the circuit breakers B$$_1$$ to B$$_9$$ are provided by overcurrent relays R$$_1$$ to R$$_9$$, respectively, some of which have directional properties also. The necessary condition for the system to be protected for short circuit fault at any part of the system between bus 1 and the R-L loads with isolation of minimum portion of the network using minimum number of directional relays is

GATE EE 2023

The most commonly used relay, for the protection of an alternator against loss of excitation, is

GATE EE 2022

A negative sequence relay is commonly used to protect

GATE EE 2011

A two machine power system in shown below. Transmission line $$XY$$ has positive sequence impedance of $${Z_1}\Omega $$ and zero sequence impedance of $${Z_0}\Omega $$

An $$'a'$$ phase to ground fault with zero fault impedance occurs at the centre of the transmission line. Bus voltage at $$X$$ and line current from $$X$$ to $$F$$ for the phase $$'a',$$ are given by $${V_a}$$ Volts and $${{\rm I}_a}$$ Amperes, respectively. Then, the impedance measured by the ground distance relay located at the terminal $$X$$ of line $$XY$$ will be given by

GATE EE 2008

In a biased differential relay the bias is defined as a ratio of

GATE EE 2006

The transmission line distance protection relay having the property of being inherently directional is

GATE EE 2004

Consider the problem of relay co-ordination for the distance relays $$R1$$ and $$R2$$ on adjacent lines of a transmission system figure. The Zone $$1$$

and Zone $$2$$ settings for both the relays are indicated on the diagram. Which of the following indicates the correct time setting for the Zone $$2$$ of relays $$R1$$ and $$R2.$$

GATE EE 2002

In an inverse definite minimum time, electromagnetic type over-current relay, the minimum time feature is achieved because of

GATE EE 2000

In a 3-step distance protection, the reach of the three zones of the relay at the beginning of the first line typically extends upto

GATE EE 2000

Reactance relay is normally preferred for protection against

GATE EE 1997

If the fault current is $$2000$$ A, the relay setting is $$50$$% and CT ratio is $$400:5,$$ the plug setting multiplier will be

GATE EE 1996

A Buchholz relay is used for

GATE EE 1992

Marks 2

A $$3$$-phase transformer rated for $$33 kV/11kV$$ is connected in delta/star as shown in figure. The current transformers $$\left( {C{T_s}} \right)$$ on low and high voltage sides have a ratio of $$500/5.$$ Find the currents $${i_1}$$ and $${i_2}$$, if the fault current is $$300$$ $$A$$ as shown in figure.

GATE EE 2015 Set 2

The over current relays for the line protection and loads connected at the buses are shown in the figure.

The relays are IDMT is natural having the characteristic
$${t_{op}} = {{0.14\, \times \,time\,\,multiplier\,\,setting} \over {{{(plug\,\,setting\,\,multiplier)}^{0.02}} - 1}}$$
The maximum and minimum fault current at bus $$B$$ are $$2000A$$ and $$500$$ $$A$$ respectively. Assuming the time multiplier setting and plug setting for relay $${R_B}$$ to be $$0.1$$ and $$5$$ $$A$$ respectively, the operating time of $${R_B}$$ (in seconds) is __________.

GATE EE 2014 Set 1

Consider a stator winding of an alternator with an internal high resistance ground fault. The currents under the fault condition are as shown in the figure. The winding is protected using a differential current scheme with current transformers of ratio $$400/5$$ $$A$$ as shown. The current through the operating coil is

GATE EE 2010

Match the items in List-$$I$$ (Type of transmission line) with the items in List-$$II$$ (Type of distance relay preferred) and select the correct answer using the codes below the lists.

List-$$I$$
$$A.$$ Short Line
$$B.$$ Mesium Line
$$C.$$ Long Line

List-$$II$$
$$1.$$ Ohm Relay
$$2.$$ Reactance Relay
$$3.$$ Mho Relay

GATE EE 2009

Voltage phasors at the two terminals of a transmission line of length $$70$$ km have a magnitude of $$1.0$$ per unit but are $$180$$ degrees out of phase. Assuming that the maximum load current in the line is $$1/5$$^th of minimum $$3$$-phase fault current. Which one of the following transmission line protection schemes will NOT pick up for this condition?

GATE EE 2008

A list of relays and the power system components protected by the relays are given in List-$${\rm I}$$ and List-$${\rm II}$$ respectively. Choose the correct match from the four choices given below

List-$${\rm I}$$
$$A.$$ Distance relay
$$B.$$ Under frequency relay
$$C.$$ Differential relay
$$D.$$ Buchholz relay

List-$${\rm II}$$
$$1.$$ Transformers
$$2.$$ Turbines
$$3.$$ Busbars
$$4.$$ Shunt capacitors
$$5.$$ Alternators
$$6.$$ Transmission lines

GATE EE 2003

The plug setting of a negative sequence relay is $$0.2$$ $$A.$$ The current transformer ratio is $$5:1$$. The minimum value of line to line fault current for the operation of the relay is

GATE EE 2000

The neutral of $$10$$ $$MVA,$$ $$11$$ $$kV$$ alternator is earthed through a resistance of $$5$$ ohms. The earth fault relay is set to operate at $$0.75$$ $$A.$$ The $$CT's$$ have a ratio of $$1000/5.$$ What percentage of the alternator winding is protected?

GATE EE 1998

The distribution system shown in figure is to be protected by over current system of protection. For proper fault discrimination directional over current relays will be required at locations

GATE EE 1993

Marks 5

The per unit voltages of two synchronous machines connected through a lossless line are $$0.95\,\angle {10^ \circ }$$ and $$1.0\,\angle {0^ \circ }.$$ Match the two sides in the following

GATE EE 1996

Type of Relay
$$A.$$ Buchholz Relay
$$B.$$ Translay relay
$$C.$$ Carrier current, phase comparison relay
$$D.$$ Directional over Current relay
$$E.$$ Negative sequence relay

Most suited for
$$P.$$ Feeder
$$Q.$$ Transformer
$$R.$$ Radial distributed
$$S.$$ Generator
$$T.$$ Ring main distributor
$$U.$$ Long over head transmission line

GATE EE 1995

The distance relay with inherent directional property is known as ________relay.

GATE EE 1995