School of Engineering Practical 1: Singapore Distribution Network Ngee Ann Polytechnic Power Systems
Operation & Design (43PSDO)
Name: Muhammad Syafiq Aslam Bin Abdullah Class: PGA1
Practical 1: Singapore Distribution Network
Objective
1 To describe the topology, characteristics of Singapore distribution network
2 To describe the layout of a typical Singapore LV substation
3 To explain safety procedures and requirements for working in substations
4 To draw single-line diagram of a distribution network
Required Equipment and Tools
1 Power & Energy Lab (23-0002-0008)
2 Laptop with Microsoft Office and optionally AutoCAD Electrical
Part 1: Singapore Distribution Network
Figure 1 shows a subnetwork of Singapore distribution network.
Figure 1: A typical Singapore distribution network
The subnetwork consists of 2 distribution source stations, SS-A and SS-B. Each distribution
source station consist of 2 units of 75 MVA 66/22 kV star-star-delta transformer. The neutral
point of the 22 kV winding is grounded with a 6.5 Ω resistor, which is used to reduce 3-
phase-to-ground short-circuit fault. The vector group of the transformer is Yyn0d11.
SP PowerGrid distributes electricity from 22 kV substations (SS-C to SS-R) via:
▪ 22 kV customer services.
Customers will have to manage its own 22/6.6 kV or 22/0.4 kV or 6.6/0.4 kV
distribution substations.
▪ 22/6.6 kV distribution transformers.
Customers will have to manage its own 6.6/0.4 kV distribution substations.
▪ 22/0.4 kV distribution transformers.
Customers will have to manage its own distribution panels or consumer units.
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School of Engineering Practical 1: Singapore Distribution Network Ngee Ann Polytechnic Power Systems
Operation & Design (43PSDO)
Each source station or substation consists of switchgear. A circuit breaker is assembled
inside each switchgear.
Figure 2 shows the internal view of a medium voltage switchgear and its single-line
representation.
Figure 2: A medium voltage switchgear and its single-line representation
A switchgear is commonly named using this 3-block notation:
Substation of the switchgear⁄Voltage level⁄Substation at the other end
Two switchgears with their name are shown in Figure 3.
Figure 3: Examples of switchgear naming
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School of Engineering Practical 1: Singapore Distribution Network Ngee Ann Polytechnic Power Systems
Operation & Design (43PSDO)
Practice, Discussion & Homework for Part 1
a) Determine the number of ring circuits in Figure 1.
Ans: 2 ring circuits.
b) If there is a cable fault between substations SS-D and SS-E, state which substation(s)
will be unsupplied. What could be done to resupply healthy but deenergized
substations?
Ans: There would be no outage, but the fault has to be repaired.
c) If the supply to switchgear SS-A/66/TF2 is disrupted due to a transformer fault in TF2,
state which substation(s) will be unsupplied. What could be done to resupply healthy
but deenergized substations?
Ans: There would be no outage, but we have to repair the fault.
d) A cable between SS-J and NP would trip the circuit breaker in SS-J/22/NP. The whole
NP will be unsupplied. Suggest a way to maintain the high supply availability for NP.
Illustrate your answer using suitable single-line diagram.
Ans: Install emergency generator in Ngee Ann to supply it if trips.
Part 2:
A 360-virtual view of the LV substation (SS-58) below Ngee Ann’s Blk 58 is available at
http://tiny.cc/ss-58. A simplified single-line diagram for SS-58 is shown in Figure 3.
Figure 3: Simplified single-line diagram for SS-58
SS-58 distributes electricity via low-voltage main switchboard LVMSB-58 and emergency
main switchboard EMSB-58. If incomer from SS-3 is deenergized, the diesel generator could
be started up to supply via EMSB-58.
The interlock ensures that the EMSB-58 could only be supplied by one source, and the
diesel generator cannot be connected to the main switchboard.
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School of Engineering Practical 1: Singapore Distribution Network Ngee Ann Polytechnic Power Systems
Operation & Design (43PSDO)
Practice, Discussion & Homework for Part 2
a) Draw a simplified floor layout of the SS-58 by
▪ naming the rooms
▪ showing locations of LVMSB-58 and EMSB-58
▪ Showing connections o 1: between incomer and transformer o 2: between
transformer and LVMSB-58 o 3: between LVMSB-58 and EMSB-58
o 4: between EMSB-58 and the diesel generator
b) State the names of all apparatuses appear on the transformer.
Part (a) layout diagram:
Part (b) Ans:
-Pressure gauge
-Oil level gauge
-Oil temperature gauge
-Winding Temperature gauge
-Off-load tap changer
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School of Engineering Practical 1: Singapore Distribution Network Ngee Ann Polytechnic Power Systems
Operation & Design (43PSDO)
Part 3 – Substation and Personal Safety Against Electrical Faults and Hazards
a) Watch the video “Working inside a Substation (138 kV – 345 kV)” from
https://www.youtube.com/watch?v=lOlWWxh9jHU and list the 3 procedure a substation
engineer arrives at a substation.
b) Search for “EMA Transmission Code 2021” (without the quote) from the Internet and
read Section 10.5 on “Isolation and Earthing Principles” from the published
document. Explained the operation requirements for isolation and earthing procedures.
c) Watch Section 10 on “Electrical Protective Equipment” in “Course 715 – Electrical
Safety for Technicians & Supervisor” from
https://www.oshatrain.org/courses/mods/715m10.html and answer the following
questions:
▪ List all required personal protective equipment (PPE) when working in substation
▪ State the purpose of electrical protective gloves
▪ Explain the purpose of insulating protective equipment (IPE) and how it is different
from PPE.
Part 4: Single-line Diagram of the 22 kV Distribution Network in the Lab Study the 22
kV distribution network in the lab. Draw the substations and interconnection among them
on a single-line diagram.
S/SD S/SA
S/SC S/SB
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