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The Power Quality Network is a database for electrical material typically used by electrical utilities and large industrial plants. This website is a portal for publishing information on equipment, structures, methods and standards related to the low, medium and high voltage electrical power systems. The information within the site is organized into an Ontology. An Ontology is a formal way of defining information entities and their interrelationships with one another.

We hope it becomes an useful tool for electrical engineers at utilities, EPC, and in industry.

The first database we have started, is with Medium Voltage Separable Cable Accessories and you can view it in the Materials Section.

Latest Articles

Current Limiting Fuses

A Current Limiting Fuse (CLF) is a fuse that has the ability to reduce the magnitude of fault current caused by a downstream fault. CLFs are typically used in high-fault-current areas to reduce fault duty on equipment. More recently, they are being used to reduce the severity of voltage sags. A Current Limiting Fuse meets the following three conditions: 1) interrupts all available overcurrents within its interrupting rating; 2) within its current-limiting range, limits the clearing time at rated voltage to an interval equal to, or less than, the first major or symmetrical current loop duration; and 3) limits peak let-through current to a value less than the available peak current.

Distribution transformers protected solely by an expulsion fuse have very low interrupting capacity, ranging between 600A and 3,500 Amps, and are subjected to higher risk of tank damage during an internal fault condition. These units also are subjected to large amounts of additional arcing and energy during an internal fault that may affect additional equipment on the distribution system. If a fault occurs that exceeds the expulsion fuse interrupting capability, the fault will continue to arc within the transformer until another protective device has time to react. This situation can increase the number of affected customers while extending the time required to restore service. The CLF high interrupting capabilities not only reduce the duration of arcing inside the transformer, but also isolate the fault to the transformer which minimizes the effects of the event.

Benefits

  • Major reduction in the depth of voltage sags and their duration compared to depth and sag when using an expulsion fuse
  • An increase in safety for workers and the public because of greatly reduced damage at the fault location

Negatives

  • High cost compared to the cost of an expulsion fuse
  • Incompatibility between fuse saving and CLF usage on lateral lines
  • Susceptibility of CLFs to damage by transients
  • An increased difficulty in coordinating with other protective devices

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Loop Feed, Single Phase, Primary Deadfront, Distribution, Padmount, Transformer, Structure

A Loop Feed, Single Phase, Primary Deadfront, Distribution, Padmount, Transformer, Structure is typically installed along feeders underground residential developments (URD's). Padmounted transformers step down the voltage to feed one or multiple service drops of the secondary bushings. Many padmounted transformers may serve a single large building, or it may serve many residences.

They housed in a locked metal enclosure that give the transformer a tamper-resistant rating. They typically rest on a concrete pad with conduit openings so that incoming and outgoing cables can be brought into the termination compartment from underground.  Almost all padmounted transformers are oil filled type.

On the primary (high) side of the transformer they will have two medium voltage bushings (H1A and H1B),  one set for the incoming feed and one for the outgoing feed. This means there are two bushings for one phase to allow the customer allow the customer to connect all of their transformers in a loop configuration.

A typical enclosure includes a tank for holding the core/coil assembly of the padmounted transformer immersed in oil or the like, and a wiring cabinet having high and low voltage wiring compartments for enclosing the high and low voltage bushings, respectively, of the transformer, etc.

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200A LOABREAK ELBOW CONNECTORS

The 200A loadbreak seperable elbow connector is suitable for connecting URD underground cable to URD transformers and switchgear. It provides a deadfront submersible cable connection. These elbows are submersible so they are especially useful in all subway and subsurface transformer primary connections, and connections to various types of equipment such as vacuum switch and interrupters.

Loadbreak and load make operations require the aid of a live-line tool (shotgun stick with elbow puller).

For application on ungrounded WYE or delta systems, the next higher voltage class product is recommended, for instance on a 15KV delta, the 25KV elbow should be used. Their ratings are always line-to-line, so a 15kV elbow will only be rated 8.6KV Line-to-Ground, so a 15kV delta will exceed the rating of the elbow.

The elbows kits are cable size sensitive due to the elbow lug needs to be crimped to the connector, and the elbow housing needs to provide a water tight seal around the cable insulation.

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