J.

Modern Technology & Engineering

Vol.2, No.2, 2017, pp.133-139

CALCULATION AND SETTING OF RELAYS IN

TRANSMISSION OVERHEAD LINES

M. Špes1*, Ľ. Beňa1, M. Mikita1

1
Technical University of Košice, Košice, Slovak Republic

Abstract. This article deals with the issue of protective relays in terms of protecting high voltage
lines. At the beginning of the article it is drawn up process to protect power lines. Consequently, it
is shown the method of calculation for a particular power line and performed the calculation for
setting the distance protection. In conclusion the following parameters for setting the distance
protection are given.

Keywords: power lines, distance protective relay, impedance, impedance characteristic.

Corresponding Author: Michal Špes, Department of Electrical Power Engineering, Faculty of

Electrical Engineering and Informatics, Technical University of Košice, Mäsiarska 74, 041 20
Košice, Slovak Republic, e-mail: michal.spes@tuke.sk

Manuscript received: 20 April 2017

1. Introduction

Power system is made up of devices which are used for the generation,
transformation and transmission of electricity. With the rapid course of the
transients it is necessary to ensure the operational safety of the electricity system
the need to use protective automatics between the advised electrical relays or the
protection terminals. In today's conditions is each important electricity devices
equipped with its protective terminal.
In terms of protecting of high voltage power lines is most commonly used
distance protection relay, which is characterized by high reliability, achieve rapid
tripping times for the extension of the automatic reclosing ensure high reliability
of power lines.

2. Disturbances in power system

The worst fault in the power system are short circuit. In terms of electrical
protection relay it is interesting how the short circuit in the electrical unit reflected
in place of built-in of protective relay. Protective relays were involved in circuits
of instrument transformers together to form filters certain symmetrical
components.
Protective relay will therefore start only upon the occurrence of certain
symmetrical components. Voltage changes in the three-phase short circuit are in
the following illustration (Figure 1).

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Figure 1. Voltage changes in the three-phase short circuit

In the place of short circuit is voltage equal to zero [1]:

UE UE UE  0 (1)
L1 L2 L3
At the beginning of power line is voltage given by following equation, [1]:
U B  I L1.Z L (2)
L1
U B  I L2 .Z L (3)
L2
U B  I L3.Z L (4)
L3

where:
IL1 is current in first phase
IL2 is current in second phase
IL3 is current in third phase
ZL is impedance of transmission lines
Equations above shows, that value of voltage is higher on the beginning of
power line. With decreasing of distance to place of short circuit occur decreasing
of voltage.
The value of current is given by the following equations [1]:
EL1
I L1  (5)
ZS  ZL
EL 2
I L2  (6)
ZS  ZL
EL3
I L3  (7)
ZS  ZL
where:
Zs is impedance of power source
EL1, EL2, EL3 is voltages of source in phase L1, L2, L3.

3. Theory of distance protection

In addressing the protection of electrical lines and which they are required
high requirements in terms of time their activities and identification of fault
location is used distance protection. The time of disconnection fault part of power

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system is given based on the size ratio of the short-circuit voltage to the short-
circuit current [1] [3].
U f 
td  f  , 1   f  Z1, 1  (8)
 If 
 
where:
td is time of disconnection of fault part of power system
Uf is short circuit voltage
If is short circuit current
φ1 is short circuit angle
Impedance measuring parts measure the distance to a fault an uncertainty of.
To prevent erroneous operation of protective relay is impedance outreach
shortened [1].
p
Z I  (0,80  0,90)  ll1  Z1  c
r1 pv (9)

where:
ll1 is length of transmission lines
Z1 is unitary impedance value in Ω/m
pc is ratio of current transformer
pv is ratio of voltage transformer
Setting of the second zone impedance reach is equal to [4]:
0,80 I
Z II  (0,80  0,90)  Zl1  Z
r1 kv r2 (10)

where:
Zr2I is setting of first level of setting
kv is auxiliary power factor
In the normal operation a starting member can not operate. The following
conditions apply [1]:
U min
Z  Z min 
r1 I max (11)

where:
Umin is lowest allowed voltage on bus bars
Imax is highest allowed current of lines
Zmin is lowest impedance of lines in operation

4. Calculation of parameters for setting the distance protection

Distance protective relay operates with measurement of fault loop of

impedance at the point of installation. Input data are the ratio of disturbance
variables and voltage and short circuit current at the point of installation of
protection. The size of the measured impedance is then compared with the
impedance of tripping characteristic. If the size of the impedance is less than or
equal to the set value of tripping characteristic, after deducting the preset time
there is an instruction of the distance protection relay to the circuit breaker. For
the calculation and setting of settings for the distance protective relay it is

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necessary to choose a power line and the location of distance protective relay in
substations [2].
In our case we chose the electric stations in Stará Ľubovňa and calculation
performance for power line V6410. The distance protective relay is a main
protection for power line V6410 and back-up protection for power lines V6411,
V6422, V6424, and V6423.
Topology of the power lines is in the following figure (Figure 2).

Figure 2. Topology of the power lines

Parameters required to calculate of setting a distance relay are in the

following tables (Table 1, Table 2) from operator of distribution system.

Table 1. Parameters of substastions

Number
Power
of power ll1 (km) Type 1 ll2 (km) Type (2)
line
lines
240 185
V1 V6410 4,323 25,706
AlFe AlFe
185
V2 V6411 26,706 4,323 240 Alfe
AlFe
240
V3 V6422 42,524 - -
AlFe
240
V4 V6424 32,346 - -
AlFe
240
V5 V6423 17,181 - -
AlFe

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Table 2. Parameters of power lines

185 240
Typ
AlFe AlFe

Rm1
0,156 0,121
km
Xm1
0,4 0,392
km
Bm1
2,86 2,92
[S/km]
Idov
486 579
[A]
Rm0
0,468 0,363
km
Xm0
1,2 1,176
km
Bm0
8,58 8,76
[S/km]
Voltage
110 110
[kV]

5. Definition of individual protection zones

The proposal itself and define the different protection zones should be based
on impedance lines to be determined by the calculation referred to in the previous
section of this article.
Impedance, which measures the relay in the place of installation is different from
the calculated effect of these errors:
• Errors caused by current and voltage transformers,
• Links non-rotating constituents due to impedance of parallel lines,
• Inaccuracies in the findings of the non-rotating component of line impedance
Protection zones shall be designed to avoid any unprotected line section.
They must also be the fulfilled condition of selectivity, failure in this section shall
be equipped with a relay in given section, not neighboring relay [2].
For distance protection located at the station Stará Ľubovňa, we have
defined the following protection zones:
Zone 1: This zone impedance is set to 85% impedance line V 6410,
Zone 2: This zone is set to 100% impedance of the line V6410 and 60%
impedance line of the line V6411,
Zone 3: This zone impedance is set to 100% V6410 line impedance, 100% V6411
line impedance and 40% V6422

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Zone 4: This zone is the backward zone and the impedance is set at 30% of line
impedance V6423,
Zone 5: This zone is a zone of reclosing and the impedance is set at 115% of line
impedance V6410,
Zone 6: The backup non directional zone is the impedance set to 100% impedance
line V6410, 100% impedance line V6411, 100% impedance line V6422.
Zone 7: This zone will not be activated.
The calculated parameters for setting the distance protection are given in the
table below where:
x1 is consequent component of the reactance
r0 is non-rotating component of resistance
r1 is consequent component of the resistence
φ is short circuit angle

Table 3. Settings of protective zones for distance protective relay I

Values Values
Zone 1 Zone 2
secondary secondary
status Active Status Active

characteristic polygon characteristic polygon

x1 (Ω) 0,5553 x1 (Ω) 1,0584

r0 (Ω) 8,0477 r0 (Ω) 1,2022
r1 (Ω) 0,2102 r1 (Ω) 0,4007
φ (°) 72,8459 φ (°) 70
direction F direction F
time (s) 0 time (s) 0,5
Values Values
Zone 3 Zone 4
secondary secondary
Status Active Status Active

characteristic polygon characteristic polygon

x1 (Ω) 1,6921 x1 (Ω) 0,1102

r0 (Ω) 1,8459 r0 (Ω) 0,1021
r1 (Ω) 0,6153 r1 (Ω) 0,034
φ (°) 75 φ (°) 75
direction F direction R
time (s) 1 time (s) 0,5

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Table 4. Settings of protective zones for distance protective relay II

Values Values
Zone 5 Zone 6
secondary secondary
Status Active Status Active

characteristic polygon characteristic polygon

x1 (Ω) 0,751 x1 (Ω) 2,2376

r0 (Ω) 0,8531 r0 (Ω) 2,3511

r1 (Ω) 0,2844 r1 (Ω) 0,7837

φ (°) 70 φ (°) 75
direction F direction -
time (s) 0 time (s) 5

6. Conclusion

This article deals with the issue of distance protective relay. As mentioned
at the outset, the speed of transients requires the use of special automatics and
protection devices. These protective devices include the distance protective relay.
This article was mentioned method of calculating the adjustment of individual
protection zones. The article concludes aspects affecting the definition and
parameters of protection zones.

References

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Košice.
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sústavách, Košice, ISBN 80-89061-73-7.
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Elektro, s.r.o., Košice,. časť III., s. 321-410. ISBN 80-89057-09-861-65-6.
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sústavy, Košice, ISBN 978-80-8073-837-2.
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