types and ratings of oil circuit reclosures 3 book 2/12. types and rati… · learning objectives...

March 31, 2005

S T U D E N T M A N U A L

Types and Ratings of Oil Circuit Reclosures

Copyright 2004 by the Training and Development Centre, SaskPower. All Rights Reserved

2 S T U D E N T T R A I N I N G M A N U A L

Prerequisites: • Oil Circuit Recloser Operating Principles Module

Objectives: Given the Construction Standards Manual, you will be able to explain the types and ratings of oil circuit reclosers (OCRs).

Rationale: Although the operating principle of an OCR is relatively simple, there are many different types and ratings. Types and ratings play a role in the proper coordination and operating of OCRs within the system.

Learning Objectives• Explain the information located on the data plate.• Describe the major types of reclosers.• Explain the purpose of coordinated system protection.• Describe the effect of oil temperature on recloser resetting.

Learning Methods• Self-learning + On-the-job• Self-learning + On-the-job• Self-learning + On-the-job• Self-learning + On-the-job

EVALUATION METHODS

• Written test• Written test• Written test• Written test

STUDENT RESOURCES

• Distribution Maps

T Y P E S A N D R A T I N G S O F O I L C I R C U I T R E C L O S U R E S 3


Learning Steps1. Read the Learning Guide.2. Follow the steps outlined in the Learning Guide.3. Clarify any questions or concerns you may have.4. Complete the Practice and Feedback.5. Complete the Evaluation.



Lesson 1: OCR Data PlateLearning Objective:Explain the information located on the data plate.Learning Method:Self-learning + On-the-jobEvaluation Method:Written test

Introduction

Each OCR has a stenciled data plate (nameplate) which is located nearthe sleethood of the recloser. The information found on the data plate isas follows:

• Manufacturer• continuous current rating• minimum trip current rating• maximum trip current rating• trip close sequence• serial number• type



Manufacturer

The manufacturer makes and supplies parts for the device. However,electric companies usually have their own apparatus maintenancedivision install the parts and make repairs.

Continuous Current Rating

The continuous current rating is the amperage rating the OCR can carryon a continuous basis. At this level, overheating and cold load pickupare not concerns.

Minimum Trip Current Rating

The minimum trip current rating is the amperage rating at which theOCR will open its contacts. Often, this value is twice the continuouscurrent rating of the OCR (ie. a 35 amp OCR will open on a load of 70amps or more).



Maximum Trip Current Rating

The maximum trip current rating is the highest amperage the OCR isdesigned to interrupt. Various OCRs have different interruptingcapabilities. An area with high fault current requires an OCR with ahigher fault current interrupting ability.

Trip Close Sequence

The trip close sequence is a code that indicates the length of time andnumber of times an OCR will remain closed on a fault.

Most OCR’s operate on a 2A2C sequence. This means given apermanent fault there will be two fast operations followed by two sloweroperations, at this time the OCR locks out.

Type

Reclosers are assigned a letter, a number, or both, by the manufacturer.The different letters and numbers which implies certain characteristics.Therefore, it is important that the same type of recloser is used duringreplacement.



Serial Number

The serial number is comprised solely of numerical digits foradministrative purposes, such as tracking and recording other importantcharacteristics of the device.



Lesson 2: Types of ReclosersLearning Objective:Describe the major types of reclosers.Learning Method:Self-learning + On-the-jobEvaluation Method:Written test

Introduction

For the proper application of reclosers, there are major factors whichmust be considered (by engineering) so that the recloser with the propercharacteristics for clearing and isolating faults is selected. Therefore,the manufacturer of reclosers have a variety of types to meet demand.

Single-Phase OCRs

These devices are commonly found in rural areas on single-phase linesand tapoffs. Kyle manufactures eight different types of single-phaseOCR’s. The interrupting ratings vary depending upon the circuitvoltage.

Each type of recloser has a range of sizes, and can be used on circuitswith different voltages. The Type H has six different sizes (the largestbeing 50 amps) and can be used on 2.4kV through 14.4kV lines. Thechart below shows the largest size and its trip rating per type of recloser.The trip ratings shown may be higher for lower voltage circuits.



Three-Phase Reclosers

A three-phase recloser has three individual units within one tank. Theseunits operate independently on temporary faults but are interlocked sothat all three units will open if a permanent fault occurs on one phase.The interlock is necessary to prevent single-phasing, a condition that canruin electric three- phase motors.



Figure 1. A three-phase recloser trips phases independently, but locks phases out concurrently.

These devices are found on three-phase circuits. There are manydifferent types of three-phase reclosers not listed below. Each type ofrecloser has a range of sizes and can be used on circuits with differentvoltages. The Type 3H has six different sizes (the largest being 50amps) and can be used 2.4kV through 25kV lines. The chart belowshows the largest size and its trip rating per type of recloser. Trip ratingsshown may be higher for lower voltage circuits.



All Type 3H and 6H reclosers shall be connected with the line adjacentto the trip counter side of the recloser. Contact the engineering staff todetermine the correct line and load connections if unknown.

Reference

For further information, please refer to the ConstructionStandards Manual, Section A-26, Apparatus.



Lesson 3: System CoordinationLearning Objective:Explain the purpose of coordinated system protection.Learning Method:Self-learning + On-the-jobEvaluation Method:Written test

Fault Current

Fault current can be described as the amount of current which flowsalong a conductor and into the earth at the fault. The value of faultcurrent varies from area to area, and depends on the circuit impedance(total opposition to current flow). The current in a circuit is equal tosource voltage divided by the impedance:

Given that a 14.4kV coil is feeding a 30 mile long 1/0 ACSR Raven line,the fault current will be higher as one moves closer to the voltage source.This is true because a shorter line equates to less impedance, whichresults in a larger amperage.

Reclosers must be capable of interrupting the fault current of a line.

Coordination

Fuses, sectionalizers, and OCRs individually meet the goals of systemprotection. They protect equipment from damage, reduce customeroutages and limit hazards to life and public property. Coordination isthe use of these items together on the distribution system. The goals ofcoordination are:

1. To give all faults a chance to be temporary by ensuring a recloseroperation.

2. To remove from service only the smallest portion of the faultedsystem on a permanent fault.

Coordinating the distribution system protection is done by theengineering department. The location and rating of all OCRs and fusesare marked on the distribution prints.



A prime location for an OCR is where a long single-phase line taps offof a three-phase feeder. With no protective device at the tapoff, a faulton the single-phase line will cause the three-phase protective device tolockout. The result is customers being fed off of the three-phase line areout of power. The use of a reclosure at the tapoff would have isolatedthe fault on the single-phase line.



As you know, the above diagram indicates the periods of time that anOCR is closed and opened on a fault. If the fault is on the load side of acoordinated fuse, the OCR and fuse will coordinate as follows:

• The recloser looks at the fault for .03 seconds.• The contacts open for 1 second.• The recloser looks at the fault for .03 seconds.• Contacts open for 1 second.• The recloser looks at the fault for .40 seconds.• The protective fuse blows and the recloser remains closed.

Given a permanent fault in a coordinated system, the fuse usually clearsduring the first long operation of the recloser. However, previouslyweakened fuses may clear sooner.

The times shown are for illustrative purposes only. The time, until trip,on the fast and slow operations is dependant upon the type of recloserand the value of the fault current.

When the permanent fault is between the OCR and the coordinatedfuses, the OCR will go through its full 2A2C operation as follows:

• A = .03 seconds• Opening time for 1 second• A = .03 seconds• Opening time for 1 second• C = .40 seconds



• Opening time for 1 second• C = .40 seconds• The recloser locks out

Engineers often call the operations “A and C curves” because a curve iscreated on a graph when time (taken for a recloser to open) is plottedagainst different values of fault current.



Figure 2. “Time” is the amount of time the recloser will look at the fault before it opens. The “A,” “B,” and “C” curves are typical for a 50 ampere recloser.



Lesson 4: Oil Temperature EffectsLearning Objective:Describe the effect of oil temperature on recloser resetting.Learning Method:Self-learning + On-the-jobEvaluation Method:Written test

Introduction

An OCR with a 2A2C rating will operate four times until lockout. Givena fault and that the OCR is reset immediately after lockout, there willonly be one slow operation. This occurs because the trip piston, beingsupported by hydraulic oil, is in a position close to the lockout latch.

Figure 3. The chamber below the trip piston is full of oil after a lockout. The time it takes for the oil to drain through an orifice depends upon the thickness of the oil.

The temperature of the oil has a large effect on how long it will take forthe oil to drain out of the chamber. The colder the temperature, the



longer it takes to regain the capability for four operations.

When resetting reclosers which are timed hydraully (OCR’s),consideration must be given to the significant increase in operating timecaused by cold oil.

Load current flowing through the series trip coil creates some heat in theoil. Thus, the load on reclosers affects their tripping and reclosing times.

Malcoordination can result at low temperatures between very lightlyloaded series reclosers and heavily loaded backup reclosers.



Summary

To summarize this module, you have learned:

• The information located on the data plate.• The major types of reclosers.• The purpose of coordinated system protection.• The effect of oil temperature on recloser resetting.

Practice Feedback

Review the lesson, ask any questions and complete the self-test.

Evaluation

When you are ready, complete the final test. You are expected toachieve 100%.



Review Questions

T / F 1. The minimum trip current rating is the point at which the OCR will open its contacts.

T / F 2. The trip close sequence refers to a code which indicates the length of time and number of times an OCR will remain closed on a fault.

T / F 3. The continuous current rating of an OCR is the highest amperage the OCR is designed to interrupt.

T / F 4. Maximum trip current rating is the highest amperage the OCR is designed to interrupt.

T / F 5. Maximum trip current rating is an amperage rating at which point the OCR will open its contacts.

T / F 6. The continuous current rating is the level at which overheating and cold load pick-up is not a concern.

T / F 7. OCRs may be single-phase or three-phase.

T / F 8. Manufacturers make a variety of recloser types, each having specific characteristics for industry needs.

T / F 9. A Type E is a single-phase recloser.

T / F 10. A Type 4H is a four-phase recloser.

T / F 11. A Type 3H is a single-phase recloser.

T / F 12. A Type 6H is a six-phase recloser.

T / F 13. A Type RVE is used on 25kV lines.

T / F 14. A Type CZE is a 72kV recloser.

T / F 15. With a three-phase recloser, the interlock is built in.

T / F 16. The Type H recloser has six sizes, the largest being 50 amps continuous.

T / F 17. OCRs are only manufactured as a single-phase type.



T / F 18. A type H OCR is a three-phase recloser.

T / F 19. A type 6H OCR is a three-phase recloser.

T / F 20. A CZE reclosure is used on 72kV circuits.

T / F 21. The interlock of a three-phase OCR is built in.

T / F 22. Reclosers are not capable of interrupting the fault current of the line.

T / F 23. In a coordinated system, the OCR will lock open if a temporary fault develops on the line.

T / F 24. Given a permanent fault in a coordinated system, the fuse usually clears during the first long operation of the recloser.

T / F 25. One goal of co-ordination is to give all faults a chance to be temporary by ensuring a recloser operation.

T / F 26. One goal of co-ordination is to give all faults a chance to be permanent by ensuring a recloser operation.

T / F 27. One goal of co-ordination is to remove from service only the smallest portion of the faulted system on a permanent fault.

T / F 28. The location and rating of all OCR’s and fuses are marked on road maps.

T / F 29. The chamber below the trip piston is full of oil after a lockout.

T / F 30. The temperature of the oil has little or no effect on the time it takes for an OCR to regain capability.

T / F 31. The temperature of the oil has a large effect on how long it will take for the oil to drain out of the chamber.



Review Question Solutions

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types and ratings of oil circuit reclosures 3 book 2/12. types and rati… · learning objectives...

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