Switchgear Arrangement, Torque Requirements, Insulation Systems & Maintenance Intervals. Mike Schmaderer

Transcription

1 Switchgear Arrangement, Torque Requirements, Insulation Systems & Maintenance Intervals Mike Schmaderer

2 Questions Feel free to interrupt There are no dumb questions

3 Just what exactly is Switchgear?

4 The term switchgear, used in association with the electric power system, or grid, refers to the combination of electrical disconnects, fuses and/or circuit breakers used to isolate electrical equipment. Switchgear is used both to de-energize equipment to allow work to be done and to clear faults downstream.

5 Substation vs Switchgear Substation Easier to maintain Easier to modify Lower arc flash incident energy Switchgear (Substation in a box) Smaller footprint Better at keeping animals out Build off sight Out of weather (maybe)

6 Open Switchgear

7 Traditional Switchgear Breakers all in the bottom May require a ramp

8 Enclosure Side View

9 Two High Construction Takes up less space Lift is required for breakers in top row

10 Combination Lift is required

11 Typical One Line

12 Switchgear One Line

13 Laid Out to Minimize Load on the Bus

14 Laid Out to Meter Generation

15 Laid Out to Facilitate Maintenance

16 Laid Out to Facilitate Maintenance

17 Fused Switches

18 Outdoor Metal Clad Switchgear

19 Arc Resistant Designed to vent energy from an arc safely away from operators Extra support Costs about 30% more

20 Arc Reduction Techniques Bus Differential Protection Instantaneous Tripping With blocking Arc Relaying Strategically placed fiber Combined with overcurrent Remote Switching

21 Things to Consider Before Ordering Gear Number of Feeders Generators Tie(s) and Bus Tie Bus Ampacity Entrance Top Entrance Bottom Entrance Throat Connected Bastard

22 Things to Consider Before Ordering Gear CTs PTs For Relaying For Metering Location For Metering For Relaying For Synchronizing Location

23 Things to Consider Before Ordering Gear Breaker Arrangement Single high Two high Location of feeders, generators, tie Continuous Current Rating of the Breaker Interrupting Capability of the breaker Must be able to interrupt max fault current Arc Flash

24 Insulation Porcelain (glass) Glastic Indoor only Polymer Skirts

25

26 Breaker -Interrupters How does the Breaker extinguish the arc? Air Blast Under Oil SF6 Vacuum

27 Torqueing Requirements

28 Torque τ = torque σ y = yielding stress of material D = bolt diameter c = coefficient of friction Yield Strength (Mpa) Aluminum 241 Steel 248 Brass 200

29 Torque US Recommended Bolt Torque Recommended Torque Size Grade 2 Grade 5 Grade S/S Bronze Brass Coarse Fine Coarse Fine Coarse Fine Coarse Fine Coarse Fine Coarse Fine #4* #6* #8* #10* / / / / / / / / /

30 Torque Torque Values = inch-lbs Bolt Size 18-8 Stainless Steel Brass Aluminum 2024-T4 316 Stainless Steel Nylon /4" /4" /16" /16" /8" " /16" /16" /2" /2" /16" /16" /8" /8" /4" /4" /8" /8" " "

31 Maintenance Cleaning Relay Testing Breakers Ductor High potential Function Testing

32 Switchgear Maintenance When is the last time that the bus and bus supports were cleaned Are the heaters working Do they get turned off Dirt and Moisture Most are hard to get out of service Even with generation Ethanol Plant Example

33 Switchgear Maintenance Moving parts seldom operate Switching load Clearing faults Generator breakers operate more often Breakers/Switches Battery Relays

34 Functional Trip Testing Electrical mechanical relays Spin the disk Microprocessor based relays Force a trip Inject current Through test switches Inject primary current Through the CT s

35 Breakers Heaters Year round Trip/Close coils Rewind motors Exercise the breaker Lubricate the Mechanism

36 Relays Monitor current and voltage Overcurrent Directional overcurrent Voltage Impedance Etc.

37 Relays Relays should be tested periodically Suggest generator and tie relays every three years Suggest feeder relays every five to six years Function of the value of the asset they are protecting Test should include a functional test of the breaker

38 Types of Relays Ice cube Interposing Lockout Electromechanical Solid state (Static) Microprocessor-based (Digital/Numerical)

39 DC/Battery System Stored Energy Battery Charger Trip coils Close coils Rewind Motors?

40 Battery Check it once a month Turn off AC breaker for one hour Monitor voltage drop Compare to previous months Don t let the voltage drop more than 10% DC rewind motors

41 Common Switchgear and Substation Issues

42 Mechanism gummed up Caused by dirt and inactivity Will not trip Common during the winter Especially in outdoor breakers Often causes a blown fuse or a trip coil to burn up

43 Rewind motor will not stop winding Broken or misaligned gear Often causes motor to burn up Pull motor rewind fuses

44 Rewind motor winds up, unwinds, and rewinds continuously Latch does not catch Caused by dirt and grim Common during the winter Especially in outdoor breakers Often causes motor to burn up Pull motor rewind fuses and lubricate latch

45 Breaker will not close after a trip Blown fuse in close circuit Burnt up close coil Lockout relay not reset Sync switch not turned on

46 Broken Pole or linkage One or more phases not making contact Current imbalance Voltage imbalance Hard on generators

47 Check voltage and current often Voltage Use voltmeter to check all three phases Use sync scope to check sync PT Current Use ammeter to check current on all three phases Multifunction meters Microprocessor based relays

48 Other things to consider Record faults Phase Time Weather conditions Interrupting rating Fault study Arc Flash

49 Once again, if you are not 100% sure, get help

50 Questions?