Smart Grid Technologies and Protection

This assignment delves into the realm of smart grid technologies, focusing on key aspects such as communication network redundancy and innovative power substation designs. It examines transformerless intelligent substations enabled by SiC IGBTs and explores various earth-fault relay algorithms for enhanced protection in low-voltage DC grids. The discussion encompasses passive-overcurrent relays, directional earth-fault relays, and performance enhancements of transformer-restricted earth fault relays.

Running head: ELECTRICAL PROTECTION SYSTEM
Electrical Protection System
Name of the Student
Name of the University
Author’s note

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Executive Summary
The substation's main purpose is to obtain power from the high voltage source that is from
the power stations. In this scenario, the Berserker Substation is focussed. The redundancy is
beneficial for restricting power interruption and regulates normal flow of current whereas the
protection relay is beneficial for securing the feeder and reducing the fault. The Earth-fault
protection along with relay coordination for the earth-fault relay has been explained
elaborately.

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Table of Contents
1. Introduction............................................................................................................................3
2. Objective................................................................................................................................3
3. Background or Network description......................................................................................4
4. Redundancy in Network design.............................................................................................6
5. Protection Equipment.............................................................................................................7
6. Protection (Overcurrent) relay setting and coordination........................................................8
Relay Co-ordination for Earth-fault Relay.............................................................................9
7. Conclusion............................................................................................................................11
8. References............................................................................................................................12
9. Appendix..............................................................................................................................14

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1. Introduction
The substation’s main purpose is to obtain power from the high voltage source
that is from the power stations. In this scenario, the Berserker Substation is focussed.
This report will highlight the equipment, design associated and also the
redundancy and the protection relay will be showcased.
2. Objective
The Berserker Substation is constructed along with the equipment incorporated
keeping in mind the following advantages it can provide-
 The primary objective of the substation is to acquire the power which flows at
a high voltage from the stations where power is generated [2].
 Gas Insulated Switchgear (GIS) technology reduces substation
accommodation to seventy per cent.
 Switchgear which involves the circuit breakers and these circuit breakers are
responsible for intervening the short-circuit current generated from the power
stations.
 Surge arresters to safeguard the switchgear from over voltages happened due
to lighting thus regulates the normal current flow [1].
 Substation automation to protect, secure and control the electrical components.
 The construction work must be comparatively simpler and cheaper and must
be flexible for an extension if required.

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3. Background or Network description
The Berserker Substation along with its component design has been highlighted
in this report (Refer to Appendix A). The major function of the substation is to acquire the
power which flows at a high voltage from the stations where power is generated [3].
Synchronous condensers are installed within the substations to enhance the power factor and
giving facilities to administer and monitor different parts of the power system.
The substations can be elaborated according to the service prerequisites and
design features. The service pre requisites include converting substations, transformer
substations and switching substations.
Transformer substations: These transformer substations are responsible for
converting power from one voltage level to other. They can be further elaborated into
distribution substations, step-up substations, secondary substations and primary grid sub
stations [6]. The step-up substations generate about 11kV and that needs to be stepped up to
the primary transmission voltage level of 220kV. The primary grid stations are situated at the
transmission lines' end and the primary voltage here drops down to secondary voltages of
66kV. The distribution sub stations are situated immediately to the consumer localities to
distribute the power of 400V, three phases or single phase to the users.
Switching substations: The switching substations generally switch the workings
of power lines without converting the voltage. Various connections are generated in between
the transmission lines.
Converting substation: The converting substation is responsible for
transforming AC to DC or vice versa [4].
i. The main substations’ components

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Isolator- When the current supply is interrupted, the isolator either makes
connections or disconnects the circuit; the isolator is basically used to break the charging
current of the transmission line.
Lightning arrester- This component is used to protect the entire substation from
the lighting fallout.
CT Metering- This equipment basically measures and keep track of the current
usage at the time when the secondary terminal [7].
Step down transformer- this device is used to convert the range of voltage
current from high to low.
Capacitor Bank- This device is generally used to enhance the power factor of
the transmission line; it basically involves the series connection of the capacitor or else the
parallel connection of the capacitor.
Circuit Breaker- It basically restricts the excess flow of current.
ii. Earthing
The substation requires proper earthing as it ensures that no potential threats
occur in the substation, so while designing a substation three voltage must be kept in mind,
they are- mesh voltage, touch voltage and step voltage [2].
iii. Layout of the substation
There are four varieties that guarantee the securities of current supply –
i. No modification is required for the maintenance of the substation
ii. Little modification is required to relocate the load to the alternate circuit.

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iii. Loss of circuit due to lack of maintenance.
iv. Loss of substation as a whole due to lack of maintenance.
iv. Various Layouts
There are various layouts for the substations, one is single busbar, and the other
one is mesh substation, one and a half circuit breaker layout.
4. Redundancy in Network design
To diminish the power interruption, power grids are rapidly increasing day by
day retrofitting substation system [1]. The retrofitting applications can be executed by the
following two structures- centralised system architecture and decentralised system
architecture.
Decentralised management architecture mainly involves system redundancy
and this redundancy can be achieved by multiple computer systems, where each computer
system executes only one operating system and one application at a time. That means only
one application and one operating system can be deployed in the physical server at a time.
Centralised management architecture involves the deployment of multiple
operating systems and multiple applications on a single physical structure. Here the server
provides the virtualisation facility, here multiple operating system and multiple applications
can be executed, so applications need not be isolated, also there is no chance of compatibility
issue [4]. Secondly, the life of the legacy software applications can be prolonged or extended
by Centralised management architecture.
Use and Advantage

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The legacy power substation is upgraded with IEDs and then those IEDs are
integrated with the substation. The task is not simple and can only be accomplished by
effective management-system redundancy [6]. Retrofitting of the power substations can be
achieved by the method.
5. Protection Equipment
Protection relays are responsible to detect the abnormal behaviours within the
system, to check the faults within the system and directs more than one circuit breaker to
explore and separate the faulty equipment and systems.
Circuit breakers fail relay is responsible to connect electric equipment and
circuits in an efficient way. They are opened or closed based on the command, they are
basically opened to suspend or clear any fault within and they have been designed in such a
way that it can make a minimal impact on the power system [3].
Multifunction relay is combined with the primary control system by configuring
few input and output points to work in between the controller and relay. This relay helps in
real time monitoring of the power system and detects the faults within the Power system. The
faults are detected basically on the monitoring of the system and monitoring involves the
couple channel monitoring, monitoring of speed, monitoring of light curtain and extension of
the relay to enhance the number of output contacts.
Neutral earth fault relay is responsible to detect the ground faults and it
immediately interrupts the circuit based on the detection of ground faults. Thus the
substation’s ground faults can be minimised [5].
Sensitive Earth fault relay also checks the earth fault or the ground fault within.
It is basically used in the substation when the earth fault is set to significantly low value.

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Capacitor Bank consists of the three element s- unit fuse, element fuse and bank
protection and this is also used to detect and mitigate the internal and external faults.
Bus Differential relay in the substation is basically implemented to detect any
faults on the busbar. It takes a huge lot of time to detect the fault and this bus-bar protection
involves Kirchoff's current law [5].
Transformer Oil and Winding Trip relay are used to identify the temperature
instantaneous temperature of the oil and windings, this can also detect the maximal rise of
temperature of both oil and windings. These temperature indicators help to regulate the
temperature of the substation.
6. Protection (Overcurrent) relay setting and coordination
Overcurrent Relay provides the earth fault protection. The Earth-fault Relay is
utilised to secure the feeder opposing the faults which are correlated with the ground. The
earth faults range from single line to ground whereas the double line ranges from double line
to ground faults [8]. Here the single line to ground faults has been shown in the following
diagram for the requirements of setting and coordination. The maximum fault current for the
a-g fault can be provided by-
.
Accordingly, it can be inferred that there can be notable variety in the earth fault
current values. They can be even beneath the load current because of large impedance to
ground. Consequently, to give protection, earth fault relays utilize zero sequence current
across phase current for fault recognition [8]. The zero sequence segments are missing in load
current or phase faults.

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Relay Co-ordination for Earth-fault Relay

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Fig1: Radial Distribution Network Diagram for Berserker Substation
(Source: [6])
Fig 2: Simple Radial Distribution System
(Source: [8])
Fig 3: Phase and Earth Fault Relay Configuration
(Source: [8])

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Fig 4: Earth Fault Relay Coordination
(Source: [8])
Relay R1 is responsible for giving protection to the earth fault at secondary side
of 2.5MVA, 11/3.3kV transformer; R2 is responsible for giving protection at bus B. There are
2 CTs, one CT that is 200:5, is linked to instantaneous relay while the other one 500:5 is
linked to inverse current relay.
7. Conclusion
It can be concluded from the above discourse that the redundancy is beneficial
for restricting power interruption and regulates normal flow of current whereas the protection
relay is beneficial for securing the feeder and reducing the fault. The Earth-fault protection
along with relay coordination for the earth-fault relay has been detailed.

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8. References
[1] Zeynal, Hossein, Mostafa Eidiani, and Dariush Yazdanpanah. "Intelligent substation
automation systems for robust operation of smart grids." In Innovative Smart Grid
Technologies-Asia (ISGT Asia), 2014 IEEE, pp. 786-790. IEEE, 2014.
[2] Mainali, Krishna, Awneesh Tripathi, Sachin Madhusoodhanan, Arun Kadavelugu, Dhaval
Patel, Samir Hazra, Kamalesh Hatua, and Subhashish Bhattacharya. "A Transformerless
Intelligent Power Substation: A three-phase SST enabled by a 15-kV SiC IGBT." IEEE
Power Electronics Magazine 2, no. 3 2015: 31-43.
[3] Hao, W. A. N. G., Y. A. O. Jian, Xuan-ni LIN, and S. U. I. Hong. "Research of the
Redundancy Technologies in the Communication Network for Distribution
Automation." DEStech Transactions on Computer Science and Engineeringwcne 2016.
[4] Ge, Xiongzi, Yi Liu, Chengtao Lu, Jim Diehl, David HC Du, Liang Zhang, and Jian
Chen. "VNRE: Flexible and Efficient Acceleration for Network Redundancy Elimination."
In Parallel and Distributed Processing Symposium, 2016 IEEE International, pp. 83-92.
IEEE, 2016.
[5] Saleh, Khaled A., Ali Hooshyar, and Ehab F. El-Saadany. "Hybrid passive-overcurrent
relay for detection of faults in low-voltage DC grids." IEEE Transactions on Smart Grid 8,
no. 3 2017: 1129-1138.
[6] Stojanović, Zoran N., and Milenko B. Djurić. "An algorithm for directional earth-fault
relay with no voltage inputs." Electric Power Systems Research 96 2013: 144-149.
[7] Davarpanah, Mahdi, Majid Sanaye-Pasand, and Reza Iravani. "Performance enhancement
of the transformer restricted earth fault relay." IEEE Transactions on Power Delivery 28, no.
1 2013: 467-474.

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[8] NPTEL: Electrical Engineering - Power System Protection, Nptel.ac.in, 2017. [Online].
Available: http://nptel.ac.in/courses/108101039/17. [Accessed: 12- Sep- 2017].

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9. Appendix
Appendix A: Single Line Berserker Substation
Fig 5: Single Line Berserker Substation