CASE STUDY: Reclosures for Power utility

How to Control the Power Grid Remotely

Power loss due to downed power lines in storms, ice build up and natural disasters (hurricane, earthquake, etc..) is a costly event. Downed overhead power lines from a tree or ice along a distribution network creates a short circuit in the network. A rapid short circuit in a power network creates two primary issues for Utility Companies: damage to power control systems and loss of revenue. Transients resulting from the short circuit have the potential to damage high value and critical power controls system such as regional substations and feeder stations. It is estimated 80%-90% of faults occur from transients due to downed overhead power lines.

It is critical for Power Utility Companies to ensure the power Grid is available to commercial and residential customers. Loss of power to customer means loss of revenue and loss of credibility.

To minimise the impact of these issues, utility companies segment the power distribution network in smaller sections using automation devices known as reclosers. Breakers can be used to divide up the network, however require significantly more power to trip (ie. less sensitive to transients), can only be placed at feeder stations/substations and also require significantly more time to reset after an event.

Reclosers require far less power to trip, can be controlled remotely and most importantly can be distributed to any point throughout the power distribution network (transformer site). Reclosers enable the network to be segmented more effectively and provide better protection of high value assets as they can react to event well up the power distribution line before a substation or feeder is affected. Recloser also provide smart power quality information that can fed back to the utilities to conduct preventative maintenance.

The business case for to automated control of reclosures easily justifies the infrastructure. Automated control of reclosures ensure minimal downtime and higher power availability for consumers even in the event of downed powerlines resulting in increase revenues and happier customers.

The Challenge – Remotely Controlling and Monitoring Reclosers

In the state of Queensland, Australia, hundreds of reclosers have been installed across the entire power distribution network. A significant number of reclosers are located along the power distribution network in the remote locations to segment the power distribution network. This is common issue 3 M2M Recloser Case Study inmarsat.com faced by utility companies. Automation through remote control and monitoring of the reclosers demands reliable telecommunications services to send and receive automation data.

The challenge for the utility company was to provide a reliable, cost effective and ubiquitous communication solution to remotely control and monitor these re-closers. The monitoring control information to and from the recloser’s were in the order of 10-20MB per month. Not much traffic, however important, time sensitive traffic.

The key communication requirements for the customer was

• high availability
• resilient in natural disasters and adverse weather conditions
• Low profile
• Easy to install and support and integrate into the network
• Secure
• Ubiquitous network with real time traffic response
• Low cost
• Low Profile single unit that can fit to a power pole

The solution

Satellite communication was the logical choice to ensure the network infrastructure is protected from local natural disaster. Critical power infrastructure control requires the reliability to maintain communication in a natural disaster. During the recent floods in the North East of Australia, cellular and terrestrial network remained down, while satellite communications remained stable.

Inmarsat’s BGAN satellite network using the Addvalue Ranger M2M terminal was the chosen satellite communication solution as it met all of the key requirements for monitoring and controlling the reclosers. The terminal was integrated easily with the utilities recloser and deployed throughout the power distribution network.

The BGAN network provides a ubiquitous solution with global coverage and availability exceeding 99.9%. It is an IP-based, cloud network; a crucial requirement for recloser control.

The comment from the utility’s Chief Telecommunications Director was “The Inmarsat network has been 100% solid and never missed a beat, our cellular networks for other services are only 60%-80% reliable.” 4 M2M Recloser Case Study inmarsat.com North Eastern Australia is a varying climate with tropical style weather and heavy rainfall in some seasons, conditions which are major factors in evaluating any remote automation solutions. The Inmarsat BGAN network operates in satellite frequency (L-band) and is unaffected by weather making BGAN the most suitable satellite solution.

The BGAN M2M Addvalue Ranger unit was selected as the preferred terminal from the Inmarsat BGAN family of products. The Addvalue Ranger being a single piece and easy to install, low profile unit with a hardened IP 66 rating was a logical choice. The picture below illustrates how the Ranger terminal is deployed and integrated with the recloser.

With the initial deployment of 100 sites increasing to 400 sites and each site consuming up to 20MB per month, Inmarsat pooled data plans were found to be the most cost effective solution in automating the reclosers. Inmarsat flexible data sharing plans enable the utility company to share data usage across all of the BGAN sites.

Using a Secure close IP virtual private network, the recloser network becomes a single extension to the Utility’s corporate network. The stringent security control provide by Inmarsat’s BGAN network provides peace of mind to any potential network intrusions and is much more robust than cellular infrastructures. The network design below illustrates how the BGAN Network was used to connect the utility company to their remote Reclosers.

Summary

The Australian Utilty mentioned in this Case Study has chosen to use Inmarsat’s BGAN M2M products and services to automate their reclosers for these primary reasons:

• Reliability
• Ease of installation
• Security
• Price/performance ratio

Training the field employees to install and support these units has been very easy and the performance has been flawless. Compared to other wireless solutions, including cellular solutions, the Inmarsat BGAN M2M solution has offered a better price to performance ratio and much stronger security.