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APPLICATION NOTE

GridSense, Inc.2568 Industrial Blvd., Ste. 110 Tel: 916-372-4945

West Sacramento, CA 95691 Fax: 916-372-4948

CHK GridSense PTY Ltd.Suite 102, 25 Angas Street Tel: +61 2 8878-7700

Meadow Bank, NSW 2114, Australia Fax: +61 2 8878 7788

gridsense.com

DistributionIQ: Battery-Free, Maintenance-Free Intelligent

Underground Fault Monitoring

INTRODUCTION

All over the world, utilities are increasing the amount of

underground cabling on their network. Underground

cables are protected from environmental changes and

extremes, remove the threat of downed power lines,

and thus help increase the reliability of power supplies.

Because of this additional reliability and safety,

underground cabling is often the distribution choice for

downtown areas of the network. While the life of the

underground network is considerably longer than the

overhead, faults and failures do occur.

Faults on the underground network pose a particular

challenge for utilities. Often used in densely populated

areas, an outage on the underground network can

heavily impact reliability scores such as Customer

Average Interruption Frequency (CAIFI) and System

Average Interruption Frequency (SAIFI). In addition,

physical constraints make tracking faults on the

underground network more complex and expensivethan tracking faults on overhead lines. These

complexities and costs leave too many underground

lines unmonitored, thus leaving too many customers

and utilities vulnerable to disturbances and outages.

Using over 20 years experience in overhead line fault monitoring, GridSense has recently

developed a new underground monitoring system that provides remote underground fault

notification along with intelligent data for determining fault locationall at a previously

unattainable price point.

REQUIREMENTS

Historically, options for underground fault detection have been non-intelligent independent

devices that lack remote capabilities. They required visual inspection to identify faults. Because

underground networks often lack AC or other power supplies, these legacy monitoring devices

were often battery-powered. But batteries require costly annual maintenance, and there is no

guarantee that batteries will not fail between inspections, leaving the network unprotected.


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Intelligent Underground Fault Monitoring 2

Utilizing extensive experience in fault monitoring, the DistributionIQ system for underground

applications leverages the same proven, tested, fully submersible, and ruggedized monitoring

platform used in the TransformerIQ solution. It detects faults and reports them remotely,

while also providing actionable data to speed analysis and diagnosis.

Recognizing the key challenges of installing products underground, GridSense based the

design on the following customer requirements:

- Monitors had to be self powered, batteryless, andmaintenance free because maintenance on the

underground network can be prohibitively expensive.

- Monitor had to be retrofitable, and quickly installed onenergized underground lines.

- Monitors had to accurately detect fault currentpassage, and have the intelligence to filter out inrushand general changes in the underground load

characteristics.

- Monitor had to have the ability to capture a variety offaults, including;

o High speed transient faults (less than 3 cycles)that may not trip protection,

o Momentary interuptions and the more typical fault-causing outages.- In order to provide intelligent, usable data, the monitor had to identify the type of fault,

phase information, fault duration, and fault current magnitude to enable distance to fault

calculations.

- Data had to be available remotely, using standard industry protocols such as DNP3 andModbus. Current remote communication options include ethernet, cellular, and utility

radio.

FULFILLMENT

Adapting existing technology, GridSense designed the compact, lightweight DistributionIQmonitoring device that attaches non-intrusively in seconds inside a pad-mounted switch or

transformer compartment. Rogowski coils encircle the outgoing underground cables to

monitor RMS and fault currents. A CT power supply is then clasped over one of the

underground cables to parasitically draw power. Communications are usually integrated into

the device and thus require little or no on-site setup.

The DistributionIQ monitor is

based on the tested, proven,

TransformerIQ platform.


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BENEFITS

Using the rugged, maintenance free DistributionIQ

platform allows utilities to identify the fault path in real

time, provides data for intelligent switching, and enablescalculation of fault location to help restore maximum

capacity to customers in the shortest possible time. All

data is transmitted to the control station via the

communications protocol of your choice, and alarms can

be retrieved via email or text message.

This new solution provides vital intelligence on network

condition that helps ensure the quality and reliability of

the power supply. Just as importantly, it allows pro-active

issue prevention, as opposed to reactive damage control.

It helps you avoid issues and outages instead of reacting

to them.

This CT power supply draws power

parasitically from existing cable,

allowing battery-free, maintenance-freemonitoring.

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