Humber Bridge – U.K.


How The World’s 7th Largest Suspension Bridge Battled Voltage Fluctuations

Case Study For Humber Bridge, U.K.

Spanning 2.22km long and carrying an average of 120,000 vehicles per week, the Humber Bridge in Yorkshire, England, is the seventh-largest suspension bridge in the world.


In an effort to prolong the achievable design life of the Humber Bridge’s suspension cables, its engineers had decided to install several state-of-the-art dehumidification systems. 


In order to install such systems, additional electrical power would have been required and would have involved the running of long supply cables from both sides of the bridge.



The Problem:
Severe Voltage Fluctuations From Seismic Shock


To provide for the optimal performance of the dehumidifiers, it was absolutely imperative to ensure the stability and quality of the incoming power supply at 415V.


Having worked on other suspension bridges in the U.K., engineers from the Electrical Contractor,  Pennine Control Systems knew all too well about the flexural and torsional vibration effects on voltage stabilisation equipment.


They were faced with several challenges including:

  • The inherent voltage drop from long cable runs
  • Incoming voltage values that had the possibility of dropping to as low as 356V
  • Heavy voltage fluctuations caused by constant load change
  • Load change which was due to continuous vehicular movement on the road decks 
  • The need for total power rating requirements of up to 420 KVA.


Based on their past experiences, it was clearly shown that the voltage stabiliser systems previously used in the UK had not proven themselves sufficient to cope with the strict requirements needed to ensure optimal performance. 


Thus, to overcome these obstacles, the team responsible for building the Humber Bridge decided to search for an Omni-voltage optimising solution – one that could reliably solve these challenges


The Ashley Edison (UK) Solution


In 2010, Ashley Edison delivered a fully customised voltage solution, to effectively accommodate the precise electrical and physical requirements of the suspension bridge.


Among the installations, it included the following series of Rack Mounted Servo-Electronic Automatic Voltage Stabilizers:

  • A Servo Electronic Digitally Enhanced Design (Servo AVR)
  • A Stepless Voltage Regulation at 415V (± 0.5% output voltage accuracy)
  • A wide input voltage tolerance – which helps stabilise a voltage swing from 340V up to 477V.
  • A Forced-Air Cooling System for improved operational efficiency
  • A Fast Response Time (<1.5ms)
  • An Inbuilt High Overload Capability (10x max current rating for 2 seconds)
  • An Independent Phase Balancing & Control: An Automatic voltage sensing & precise regulation to ensure individual phase voltages remain stable – from no load to full load.
  • A Class II SPD – For Lightning Surge Protection
  • A Rack Mounted Enclosure
  • An AquaStop – A Protective PCB coating against moisture ingress
  • A Transient Voltage Surge Protection (TVSS) helps to protect critical loads against harmful high energy surges, transients, and spikes.


The Complete Solution comprises the following:

  • Automatic Voltage Stabilisers (Model: SES Series)
    • 75 KVA x 4 units
    • 60 KVA x 2 units




The Result


Since Ashley Edison’s delivery of this solution, it has helped to successfully unlock the desired operational outcome in the bridge’s dehumidification systems, which has enabled the load to enjoy constant and stabilised incoming voltages – regardless of load change or unbalance.


The upgrading project for the Humber Bridge was completed 1 year ahead of schedule and ever since, has been able to achieve optimised operational efficiency.


Today, all 6 units of the Automatic Voltage Stabilisers delivered have still proven to be a success in not only preserving but revitalizing the significance and heritage of a 40-year-old landmark in the U.K.


To learn more about voltage optimisation for bridge and tunnel applications, drop us an email at [email protected].


For more case studies on how other Governments have also adopted these advanced voltage regulating technology, read about their projects here.

Humber Bridge U.K.
AVR | 75KVA & 60KVA
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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.