Singapore Power (SP Group) – East West Transmission Cable Tunnel Project


Emerging Voltage Drop Solution Saves National Grid Provider Millions



Case Study For Singapore Power Cable Tunnel Project

In efforts to sustain the reliability and security of electricity networks, National Grid Operator, Singapore Power – completes a $2.4-billion project, spanning a 40km network of three tunnels built to house 1,200m of transmission cables.


The objective was to ensure voltage values at the load end were kept within the maximum allowable voltage drop levels at 4% of 400/230V (376V / 216.2V).



The Problem:
Voltage Drop Problems Over Long-Distance Cables 

The conventional method of overcoming voltage drop in long-distance transmissions is to use sufficiently sized cables to cater accordingly. These cables are expensive and can amount to a hefty sum of money.

In 1 portion of the project alone, the original electrical design utilising conventional methods (of increasing the quantity and sizing of cables) would have amounted to more than $9 million in cable costs.

What was required to overcome the key issue of voltage drop and high cable costs – was a solution that is efficient and cost-effective.


The Ashley Edison (UK) Solution 

Ashley Edison identified that the following challenges had to be resolved – while meeting the client’s requirements:

  • The voltage drop values to be compensated for was an estimated 96V (almost 25% voltage drop).
  • With conventional isolation transformers, the number of power cables would have cost an additional estimate of more than $9 million.
  • The cost of these cables did not make financial sense because the loads were non-essentials (such as lighting and pumps).
  • Space limitations of housing the (originally planned) number of power cables.

Upon careful investigation and meeting requirements, Ashley Edison recommended that the MVSI series – Magnetic Induction Automatic Voltage Stabilizers be installed just before every load end. The Ashley Edison team is involved in implementing the following setups to eliminate the effects of inherent voltage drop:


Small Footprint, Huge Savings

In 2016, Ashley-Edison implemented a plug & forget solution to boost low voltage levels at the end of the tunnel – while regulating and maintaining optimum output voltage, regardless of load change. 


Additionally, with the benefits of having a drastic reduction in the number of cables required, lesser space in the tunnels is required for the new and optimised cable configuration. 


The MVSI Series – Automatic Voltage Stabiliser offers a compact, industrial-grade protection against voltage drop, with negligible maintenance. These voltage stabilizers are based on the magnetic induction design, which boasts reliability, and low operating costs for rugged applications. The MVSI Series provides ± 1.5% regulation accuracy, adhering to voltage drop standards (± 4%). 



Constant & Optimised Voltage Compensation

This specified Automatic Voltage Stabiliser series includes:

  • Magnetic Induction, Brushless Technology
  • Non-Contact design for high reliability and virtually maintenance-free usage
  • Forced-Air Cooling for improved operational efficiency
  • Independent Phase Balancing & Control: Automatic voltage sensing & precise regulation to ensure the individual phase voltages remain stable – regardless of load change or unbalance.
  • Exceptionally wide input voltage tolerance that compensates high voltage drop values from 280V, and covers high voltage values up to 460.
  • Transient Voltage Surge Protection (TVSS) to protect critical loads against harmful high energy surges, transients and spikes.


The Complete Solution comprises of the following 12 units:

  • Automatic Voltage Stabilisers (Model: MVSI Series, ± 25% input voltage tolerance)
    • 200 KVA x 2 units
    • 300 KVA x 6 units
    • 400 KVA x 2 units
    • 500 KVA x 2 units

Solving voltage drop



The Results

As expected, the fitting of the Magnetic Induction Automatic Voltage Stabilizers ensures that the load end is stabilised within voltage drop requirements – while maintaining voltage values constant, from no-load to full-load.


This solution also enabled a much more simplified power cable configuration saving precious time and resources on cable installations.


Adopting this configuration has helped Singapore’s National Grid Provider save millions of dollars that would have otherwise been spent on excessive cabling costs.


  • Estimated total distance between Point Of Supply and Point Of Installation: 7.4 km
  • Max Design Current: 134.33 A
  • Point Of Supply: 500V
  • Desired Voltage Value At Point Of Installation: 400V
  • Cables Used: XLPE / SWA / PVC / Armoured Cables



Today, Ashley Edison continues to provide comprehensive support solutions to this major project, ensuring clean and regulated incoming voltages to all major parts of Singapore.


To learn more on how to eliminate voltage drop issues the cost-effective way, drop us an email at sales@ashleyedison.com.


For more case studies on how Formula One Singapore Grand Prix has also adopted these industry techniques, read about their project here.


Singapore Power (SP Group)
AVR | Up to 500KVA, 12 units


From brownouts to severe voltage fluctuations, Ashley Edison takes care of all your power needs by delivering optimised, stable voltage supply to your electrical system.


Curious to learn more? Get in touch with us. We’ll get back to you with a quote or solution within 24 hours and put all your questions to rest.

ASHLEY Edison International LTD
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Three Phase

SESL-H-3P-S Model
Large Capacity Rating
200 to 2,000 KVA


Enclosure 335
1000W x 1300H x 580D (mm)
250~300 KVA ± 15%
120~200 KVA ± 20%


Enclosure 336
1280W x 1480H x 660D (mm)
400 KVA ± 15%
250 KVA ± 20%


Enclosure 337H
1880W x 1950H x 880D (mm)
500 KVA ± 15%
300 KVA ± 20%


Enclosure 339
1470W x 1950H x 1340D (mm)
600 ~ 1,500 KVA ± 15%
400 ~ 1,000 KVA ± 20%
300 ~ 750 KVA ± 25%
300 ~ 600 KVA ± 30%

Three Phase

SES-H-3P-S Model
Added I/P Breaker Protection
60 to 1,000 KVA


Enclosure 333
490W x 800H x 990D (mm)
≤ 100 KVA ± 15%


Enclosure 334
540W x 900H x 1000D (mm)
120 – 150 KVA ± 15%


Enclosure 335
1000W x 1300H x 580D (mm)
180 – 300 KVA ± 15%
120 – 200 KVA ± 20%
120 – 150 KVA ± 25%


Enclosure 336H
1880W x 1480H x 660D (mm)
400 KVA ± 15%
250 KVA ± 20%
180 ~ 200 KVA ± 25%


Enclosure 337H
1880W x 1950H x 880D (mm)
500 KVA ± 15%
300 KVA ± 20%
250 KVA ± 25%


Enclosure 339H
2170W x 1950H x 1340D (mm)
600~1,000 KVA ± 15%
400~600 KVA ± 20%
300~400 KVA ± 25%

Single Phase

SES-H-S Model
Added I/P Breaker Protection
1 to 100 KVA

Enclosure 102
270W x 460H x 490D (mm)
≤ 20 KVA ± 30%
≤ 15 KVA ± 20%
≤ 10 KVA ± 25%
≤ 10 KVA ± 15%

Enclosure 103
400W x 580H x 500D (mm)
25 KVA ± 15%
20 KVA ± 20%
15 KVA ± 25%

Enclosure 332
380W x 670H x 780D (mm)
30 KVA ± 15%

Enclosure 333
490W x 800H x 990D (mm)
40 ~ 50 KVA ± 15%
25 ~ 30 KVA ± 20%
20 ~ 25 KVA ± 25%
15 ~ 20 KVA ± 30%

Enclosure 334
540W x 900H x 1000D (mm)
60 ~ 75 KVA ± 15%
40 ~60 KVA ± 20%
30 ~ 50 KVA ± 25%
25 ~ 40 KVA ± 30%