Singapore Power – 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 Stabilisers 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 stabilisers 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

Magnetic Induction Voltage Stabiliser



The Results

As expected, the fitting of the Magnetic Induction Automatic Voltage Stabilisers ensures that the load end is stabilized 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 [email protected].


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
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Stay Safe With Greater Protection

As safety is our utmost priority, Ashley Edison prepares for every scenario possible
—taking the puzzle out of your protection.

Designed And Engineered With Safety In Mind

We leave nothing to chance when it comes to larger capacity units (≥400KVA). By installing high-quality protective acrylic shields in front of live parts, we ensure the safety of your personnel at all times. For enhanced protection during installation, all distances between uninsulated metal parts, busbars, and cable sizes are compliant with IEC61439-1 and IEC 61439-2 guidelines.

Outfitted with fireproof cable trunking, this protective solution safeguards against long fire exposure even in hazardous areas and explosive atmospheres—providing maximum safety for mission critical applications.

Fuss-Free Installation. Seamless Operations.

To ensure ease of installation, Ashley Edison addresses the concerns of contractors and installers by keeping it simple.



We keep the installation process simple and streamlined by allowing sufficient working space for installers. Taking the nut and bolt intrusions into consideration, we ensure that the distance between the uninsulated metal parts, the busbars, and cable sizes are compliant with IEC61439-1 and IEC 61439-2 guidelines.


Even in units with larger capacities, all busbar terminals are clearly marked out, and well positioned in line for easy identification of individual input and output terminations. Installation of these terminations are similar to those practised in high voltage transformers.

Easy Maintenance

Annual Ocular Maintenance
Visual Inspection 230

Conduct Visual Inspection On Voltmeter:

Ensure reading is set to your desired set output voltage value (e.g. 230V).

LED Status

Ensure LED Status Indicators are at “Normal”.

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Visual Observation Of Variable Transformer Surface:

Use airbrush for dusty environments if necessary.

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Visual observation if carbon brush is not worn out.

Moving Motor

Conduct visual inspection to check variable transformers are all regulating (moving).


Accuracy. Beyond Imagination.

The digitally enhanced Ashley Edison MBB Card ensures pinpoint voltage stabilisation against the most erratic anomalies, allowing you to protect precious uptime, effortlessly. Harnessing ultra precision capabilities to produce some of the tightest output voltage tolerance available in the industry, the Ashley Edison MBB Card delivers ±0.5% voltage accuracy, enabling your load equipment to enjoy optimal voltage supplies, regardless of load change in your electrical system.

Expert Digital Control

Utilising the advantageous measurements of true RMS, the Ashley Edison MBB Card’s reads both perfect, sinusoidal waves, as well as complex, distorted non sinusoidal waves—up to 0.1V accuracy. Coupled with lightning fast response time of 1.5ms, this expert digital control feature equips your load with total voltage protection that is precise, continuous and ultra responsive.

AE Digital Control Display_230v

Universal Presettable Function

The Universal Presettable Function onboard the Ashley Edison MBB Card allows seamless control of your desired output voltage value on all 3 Phases—with just a touch of a button. This multifunctional feature enables each AVR to fully operate with just 1 card, instead of separate cards for each individual phase. Fitted LED Output Voltmeter Display and Alert Indicator better facilitates easy status monitoring while performing maintenance on your AVR.


Microcontroller Unit (MCU)

MicroController Unit (MCU) helps you to deliver high speed and reliable efficiency in the AVR’s operations with less heat generation and reduced power consumption. Used in Supercomputers, Surface Mount Technology (SMT) allows components in the Ashley Edison MBB Card to be aligned closer together, creating a more compact and lightweight end product. Additional safety wire-to-board feature establishes fail-proof connectivity between circuits—so you can work safely on your AVR.