Emerging Voltage Drop Solution Saves Grid Operator $9.4Million in cable costs
13 Sep 2021
Est Reading time: 9 minutes
“What is voltage drop? How do I calculate it? And why does it cost a fortune to solve this problem!?”
In most electrical design processes, overcoming this problem can be an extremely costly affair.
The goal is to satisfy the maximum allowable voltage drop in the electrical system, no matter the size of the load.
Yet the existing solutions to long-distance cable runs are causing a significant dent in project budgets.
So if you’re looking for practical ways to finally put an end to your voltage drop woes…
You’re in the right place.
In this article, we reveal our “No BS”, field-tested methodologies on how you can successfully eliminate voltage drop, for good.
To kickstart your journey, it is crucial to first understand the what’s and how’s of voltage drop.
Let’s get started.
What Is Voltage Drop?
A voltage drop in an electrical circuit typically occurs when a current passes through the cable.
It is related to the resistance or impedance to current flow with passive elements in the circuits including cables, contacts and connectors affecting the level of voltage drip.
So the longer the length of the cable (or circuit), the greater the voltage loss.
Let’s take a look at this simple, step-by-step method to calculate your voltage drop.
Step 1: Take the value from the volt drop table (mV/A/m)
Step 2: Multiply the ACTUAL current in the cable (NOT the current rating)
Step 3: Multiply by the length of run in METRES.
Step 4: Divide results by 1,000 (to convert millivolts to volts)
Here’s an example of how the formula works – just for you:
Voltage drop (VD) = (mV/A/m x I x L) / 1000)
or
Voltage drop (VD) = (Step 1 x Step 2 x Step 3) / Step 4)
Think of the water that flows out of a tap and then down a long hose.
The farther away you get from the tap, the weaker the stream of water will be that flows out of it.
The same is true of electricity through wires:
“The farther the electricity gets from the source, the weaker the current will be.”
So now that we have a better understanding, let’s deep dive into more details.
Maximum Voltage Drop Allowed In Australia
In most parts of Australia, the nominal single phase supply voltage is 230 volts +/- 6%, this represents a range between 216.2 and 243.8 volts. (With the exception of Western Australia remaining at a nominal voltage of 240V +/- 6%).
As specified in clause 3.6.2 of AS/NZS 3000:2018 on standard installations, the maximum permissible voltage fall between the point of supply and any point of the installation is as follows:
Here’s a Rule of Thumb.
The following voltage drop limits can be used as a guide to assist with design:
In the electrical world where the threat of voltage drop is persistent and inherent.
These problems can also cause total distress to engineers.
So, this leads us to a very important question…
What is the negative impact on your equipment?
(The consequences will shock you…)
Disastrous Consequences Of Voltage Drop
Industry studies show that a 20% voltage drop lasting just 50 seconds can be extremely detrimental to your equipment’s health.
The outcomes can vary from horrifying equipment malfunction to complete facility downtime.
Here are 9 harmful consequences of voltage drop:
- Excessive voltage drips in a circuit can cause lights to flicker or burn dimly, heaters to heat poorly, and motors to run hotter than normal and burn out.
- Intermittent operation — Equipment in operation may shut down when it detects a noticeable voltage drop.
- Motors can’t start up — Appliances that require higher in-rush current levels may not start up as the voltage is below their minimum operating power level.
- Low voltage causes improper and erratic operations in your equipment.
- Over time, the damaged equipment stops working and eventually becomes completely useless.
- Blown Fuses & Tripping Circuit Breakers — Remember that P=VI so if “V” is low, an appliance may increase its “I” to reach its desired power level. When multiple loads on a circuit increase their current consumption, it could cause the safety mechanism to trip.
- When voltage fall is too steep, it can cause the load to work harder with less voltage pushing the current. This leads to POOR efficiency and wasted energy.
- Prolonged supply of low voltage and high resistance may result in fire. Fire causes destruction which may prove fatal.
- Inconsistent lighting levels — Street lighting design must take into account the gradual reduction in voltage level as a 5% drop in voltage can be noticeable on lighting levels.
These undesirable problems can post a challenge to electrical engineers.
But what exactly causes voltage fall to happen?
Let’s find out below.
What Causes Voltage Drop?
You may want to sit up for this.
Common challenges when trying to eliminate voltage drop, is the lack of understanding of what causes it.
In an environment with no room for mistakes, engineers leave nothing to chance. No guesswork, no trial and error.
Here are the 6 determining factors that cause voltage drop to happen:
- Long Distance Cable Runs - Shorter conductor length will have less voltage drop and an increased energy efficiency than longer conductors because it has the huge advantage of a shorter distance to travel.
- Inadequate Diameter of the Conductor (size or gauge of conductors) - Conductors with smaller diameters (thinner) will result in bigger voltage drop than conductors with bigger diameters (thicker) of the same length.
- Type of Material of the Conductor - Copper conducts electricity better than aluminum. It is more efficient and has the ability to endure the high pressure of electrical force.
- Temperature of the Conductor - Most conductive materials will increase their resistance because of an increase in temperature.
- Current Carried By The Conductor (Ampere Load) - Voltage drop drastically increases on a conductor with an increase in the current flowing through the conductor.
- Connections in the circuit - Poor connections in splices or when connecting conductors to terminals.
Now that you have a better understanding of all the primary conditions that cause voltage drop.
You would be wondering.
How Can I Minimise Voltage Drop?
Well, your search is finally over.
There are basically 2 ways of overcoming this issue:
- Conventional ways of minimising voltage drop.
- Adaptive way to eliminate and save.
Let’s investigate..
#1. Conventional ways of minimising voltage drop.
These methods have been the default solutions for minimising excessive voltage drop:
- Compensating voltage drop using larger cross-sectional sized cables. This offers less resistance / impedance to current flow.
- In power distribution systems, a given amount of power can be transmitted with less voltage drop if a higher voltage is used.
- Increasing the quantity of the cables will decrease the resistance – causing voltage drop to decrease, and increase your overall efficiency. (This will also lower overall power loss!)
If you’re at the preliminary design stage of your project, you may find that the costs involved in these conventional methods will make a significant dent in your budgets…
And that’s how some processes come to a screeching halt.
On the other hand, ensuring a regulated and stabilised voltage supply should always be a priority.
After all, the failure of your system’s assets is the very risk that must be mitigated if not eliminated..
#2. Adaptive way to eliminate and save.
So how are grid operators and consultants effectively eliminating voltage drop, saving millions on cable cost?
Case Study
(2017 Underground Transmission Cable Tunnel Project)
- 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
In efforts to sustain the reliability and security of electricity networks, a Grid Operator 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).
However, in just one portion of the project alone, the original electrical design utilising conventional methods of increasing the quantity and sizing of cables:
Would have amounted to an estimated $12 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:
And in 2017, Ashley-Edison’s Automatic Voltage Regulators were deployed to:
- Boost low voltage levels at every load end of the cable tunnel.
- Regulate and maintain an optimum output voltage, even if the load changes.
Through a carefully designed configuration, over a dozen Automatic Voltage Regulators have helped achieve the objectives and save over $9 million dollars in project budget.
These savings solely came from what would have otherwise been spent on cabling costs.
In Conclusion
The key to effectively eliminate voltage drop problems is essentially having a solution that is both on point, and on budget.
If you need help solving your voltage problems or you wish to explore more innovative ways to optimise your electrical system, let our expertise be your guide.
Are you a firm believer of conventional engineering methodologies?
Are you against the idea of other field-tested alternatives to solve your power problems?
To learn more about how Automatic Voltage Regulators can benefit your electrical design, drop us an email at sales@ashleyedison.com and we’ll be happy to help you chart the best solution for your power needs.
P.S. Want to know how other esteemed companies are overcoming their power problems?
Click here to find out more.
Sources:
https://www.standards.org.au/engagement-events/flagship-projects/wiring-rules
https://www.todayonline.com/singapore/deepest-tunnels-spore-start-carrying-electricity-end-2018
https://www.spgroup.com.sg/cable-tunnel/About%20The%20Project.html
https://electrical-engineering-portal.com/cable-sizing-of-sub-main-circuits-working-examples