ETP 2161C Week #1 HV Power Circuit Breakers (Text book ref.) This course will refer to the following text book, chapter and page #. Power Line Worker: Substation, level 3 trainee guide. Please study and review over the course of the next 16 weeks, Module #3, Medium and High Voltage Equipment Installation. In this module #3, please read and review pages There will also be an instructor prepared custom Power Point each week that will compliment this text book. Thanks, Bob Seigworth.

ETP 2161C Week #1 HV Power Circuit Breakers (HV Breaker semester high lights) This semester we will cover the following topics in class: Electrical safety in general. HV Power Circuit Breaker safety. Discuss fall protection, stored energy, and environmental concerns. HV Power Circuit Breaker basics. (What is a Breaker?) HV Power Circuit Breaker applications and design principles. HV Power Circuit Breaker construction, maintenance, and trouble- shooting. HV Power Circuit Breaker insulating fluids and gasses.

ETP 2161C Week #1 HV Power Circuit Breakers (HV Breaker discussion) This week we will cover the following topics in class: Electrical safety in general. HV Power Circuit Breaker safety. Fall protection Stored energy precautions and hazards Environmental concerns (Oil, SF6 gas, SF6 gas decomposition products) Discuss electrical shock and radiation from hi-potting VCB breakers. Discuss proper equipment grounding practices.

ETP 2161C Week #1 HV Power Circuit Breakers (Pre-Job Briefing) Begin with Safety PJB. Safety and HP topics: Have a questioning attitude. (Don’t just assume) Before operating a specific piece of equipment, read and understand the operators manual. Follow all “lock out tag out” procedures before attempting to work on a HV breaker. When working off the ground more than 6 feet, fall protection training is required, as well as fall protection in the form of a body harness and lanyard.

ETP 2161C Week #1 HV Transformers (Employee fall protection.) This course will refer to the following OSHA rules and guidelines for employee fall protection when working over 6 ft above the ground such as when an employee would be working on a HV power transformer either performing construction, maintenance, and trouble shooting procedures (b)(15) "Walking/working surfaces not otherwise addressed." Except as provided in (a)(2) or in (b)(1) through (b)(14), each employee on a walking/working surface 6 feet (1.8 m) or more above lower levels shall be protected from falling by a guardrail system, safety net system, or personal fall arrest system (c) "Protection from falling objects." When an employee is exposed to falling objects, the employer shall have each employee wear a hard hat and shall implement one of the following measures:

ETP 2161C Week #1 HV Power Circuit Breakers (OSHA fall Protection statutes)

ETP 2161C Week #1 HV Power Circuit Breakers (Fall Protection) Full body harness for fall protection.Safety lanyard

ETP 2161C Week #1 HV Power Circuit Breakers (Fall Protection)

ETP 2161C Week #1 HV Power Circuit Breakers (What is a Power Circuit Breaker) Modern HV power circuit breakers are a heavy duty “electrical” switch designed to break fault current, perform switching duties (open and close), and along with bushing current transformers serve to provide protective relays with secondary current inputs for metering and protective relaying. There are many types of HV power circuit breaker designs and applications, and use many different types of technology to perform the duty of interrupting fault current, or abnormal electrical conditions. HV power circuit breakers are considered “Load breaking devices”.

ETP 2161C Week #1 HV Power Circuit Breakers (What is a Power Circuit Breaker) For a B.E.S. Bulk Electric System to operate properly, it must be capable of switching circuits “IN” and “OUT” as needed. The electrical devices most commonly used to perform the switching function are power circuit breakers. In the simplest sense, a circuit breaker interrupts a circuit by physically moving electrical contacts apart to stop the flow of electrons or current. Power circuit breakers have 2 functions: 1. To interrupt circuits under normal load conditions. 2. To interrupt circuits under fault or abnormal conditions.

ETP 2161C Week #1 HV Power Circuit Breakers (HV breaker applications) HV Power Circuit Breakers are normally energized at rated electric system or B.E.S. operating potentials from 4KV – 765KV. Power circuit breakers use different insulating mediums such as oil, SF6, Vacuum, and air. The breaker mechanism which serves to store energy for future operation of the breaker poles and contacts, and internals has dangerous operating hazards if not respected. Stored energy in the form of compressed air, hydraulic pressure, charged springs, magnetic attraction, and manually supplied energy by a switchman.

ETP 2161C Week #1 HV Power Circuit Breakers (HV breaker applications) HV Power Circuit breakers require stored energy sources for future pending operation of the primary voltage contacts to either open or close with respect to the contacts themselves. The stored energy typically comes from a high energy mechanical mechanism either through Pneumatic, hydraulic, spring, or magnetically operated mechanisms that take stored energy and convert that into directional force. Think of a HV breaker mechanism as a large “RAT” trap with a large spring that is charged just waiting to go off. The rat trap is a stored energy device, and requires someone or something to set it off, and releases all that stored energy.

ETP 2161C Week #1 HV Power Circuit Breaker (Stored energy Mechanisms.) Stored energy in the form of compressed springs. Stored energy in the form of Hydraulic accumulators.

ETP 2161C Week #1 HV Power Circuit Breaker (Stored energy “Pneumatic Mechanisms”.)

ETP 2161C Week #1 HV Power Circuit Breaker (Stored energy “Magnetic” Mechanisms.)

ETP 2161C Week #1 HV Power Circuit Breakers (Stored energy mech’s) When working on or around stored energy mechanism for either construction, maintenance, or trouble shooting purposes, remember to lockout / tag out the stored energy before working on it. The stored energy and mechanism can take off fingers, hands, or worse if the mechanism where to operate with your fingers in the mechanism itself. If the mechanism is charged with either spring pressure, air pressure, or hydraulic pressure, discharge the energy before working on any part of the HV breaker or mechanism.

ETP 2161C Week #1 HV Power Circuit Breakers (HV Breaker environmental concerns) When working with OCB oil circuit breakers, their is specific protocol for working with oil filled devices with respect to the environment. Care should be taken when pumping and filtering of OCB mineral oil with a filter press, hoses, and oil storage tanks and equipment. Dangerous static electricity buildup can occur when pumping oil, and care taken to ground all equipment including HV equipment, filter press and tankers. Remember that 1 drop of oil on the ground is too much with respect to leakage and spilling of the oil. There are state and federal laws and guidelines that must be followed for handling and processing oil. Discuss safe handling and / or reclaiming of SF6 gas with a reclaiming trailer.

ETP 2161C Week #1 HV Power Circuit Breakers (HV Breaker “OCB” environmental concerns)

ETP 2161C Week #1 HV Power Circuit Breakers (HV Breaker environmental concerns) When working on SF6 circuit breakers, there is specific protocol for working around SF6 filled devices with respect to the environment. Always use approved work methods when pumping and filtering of SF6 gas, hoses, reclaiming trailer, and equipment. There are state and federal laws and guidelines that must be followed for handling and processing of SF6 gas. SF6 recovery refers only to the process of removing the gas from the unit or breaker. Recycling SF6 gas refers to reusing the gas with only minor field filtration required. Reclaiming the SF6 gas defines a more extensive process that must be done at the gas plant.

ETP 2161C Week #1 HV Power Circuit Breakers (HV Breaker environmental concerns) When working on SF6 circuit breakers, there is specific protocol to not only the environment, but also personnel safety. With regard to a SF6 gas filled power circuit breaker, the SF6 gas is used for not only insulation, but also for the ARC quenching medium that extinguishes the arc. SF6 breakers that have operated for electrical faults typically will decompose the SF6 gas, and creates a white toxic powder substance that lies in the primary interrupter chambers. This white decomposition powder should not be inhaled or ingested, and can cause serious health concerns and hazards.

ETP 2161C Week #1 HV Power Circuit Breakers (HV Breaker “SF6 Gas” environmental concerns)

ETP 2161C Week #1 HV Power Circuit Breakers (HV Breaker environmental concerns) When working with vacuum bottle circuit breakers, there is specific protocol for working around vacuum bottle interrupters. Be aware of electrical Hi-potting shock dangers, and possible “X-ray” radiation concerns from placing excessive AC hi-pot voltage on the vacuum bottle itself. Typical vacuum bottle AC high potential testing involves specially made HV equipment and testing leads that will test for dielectric integrity. Use extreme caution when testing vacuum bottles at 35-60KV. Always read and use approved work methods when performing this type of work. Barricading is recommended to keep people out of the test area when HV testing.

ETP 2161C Week #1 HV Power Circuit Breakers (HV Breaker “vacuum breaker” concerns)

ETP 2161C Week #1 HV Power Circuit Breaker (Stored energy “Magnetic” Mechanisms.)

ETP 2161C Week #1 HV Power Circuit Breaker (HV breaker equipment grounding.)

ETP 2161C Week #1 HV Power Circuit Breakers (HV Breaker “grounding” practices) It is imperative that all HV equipment including HV circuit breakers be grounded properly, and in accordance with NESC National Electrical Safety Codes. The importance of proper equipment grounding or bonding to earth is critical, and keeps the HV apparatus case grounded and electrically at the same potential as the substation ground grid itself. If HV equipment were not grounded properly, personal could be shocked with a difference in potential that could prove lethal! Caution: Before touching HV apparatus, make sure that the equipment ground connection is attached not only to the apparatus, but also the grounding grid itself!

ETP 2161C Week #1 HV Power Circuit Breakers (HV Breaker “grounding” practices) Proper grounding of HV apparatus including power circuit breakers is critical for the proper operation of all electrical protection schemes. Protective relays rely upon CT current transformers in the HV power circuit breakers, and must be installed properly in equipment that is grounded properly. If the circuit breaker was not grounded properly, then the CT could fail, or improperly reproduce the secondary output current due to not all primary fault current on that particular breaker returning to the substation ground field itself in which the circuit breaker itself is connected to.

ETP 2161C Week #1 HV Power Circuit Breakers (HV Breaker “safety” practices) Close this weeks lesson with a safety message. Discuss the importance of looking to see if HV equipment is grounded to the station ground grid before touching or servicing the HV equipment. Discuss difference in potential or “shock” hazards within the electric utility environment. If you discover that equipment grounding has been compromised, it is best to de-energized the equipment before grounding repairs are made.