I. Introduction
As plants, buildings and electrical loads become larger, the economics of using higher voltages for distribution and for motor control become more compelling. PEARL's Section 2200, Medium Voltage Circuit Breakers & Starters, addressed here has both circuit breakers and motor starting contactors. While these devices are different function, the inspection, reconditioning and testing of all of these devices have enough in common that PEARL believes in appropriate to group them together.
Section 2200, Medium Voltage Circuit Breakers & Starters includes the following standards:
- 2210 Medium Voltage Circuit Breakers Air
- 2220 Medium Voltage Circuit Breakers Vacuum
- 2250 Medium Voltage Contactors Air
- 2260 Medium Voltage Contactors Vacuum
II. Components
Medium voltage circuit breakers & starters are relatively complex electromechanical devices with a large number of parts, assemblies and subassemblies. Each has:
- Contact assemblies
- Closing coils or motorized closing systems
- Arc protection, either by arc chutes or by vacuum bottles
- Electric opening system
- Electric closing system
- System of primary and secondary disconnects
III. Testing and Inspection
All PEARL Standards begin with the definition of the term "Reconditioning" as "the process of returning electrical equipment to safe and reliable operating condition based upon the design of the original manufacturer at the time of manufacturing." This is followed by identification of the required information tables to be found in section 6000 of the standards.
Section I for PEARL Section 2200, Medium Voltage Circuit Breakers & Starters, begins with reference table identification and identification of the test equipment necessary to complete the standard, including:
- Insulation Resistance Test Set (Megohmeter) 2500 Vdc minimum
and
- AC Overpotential Test Set (Hipot) or
- DC Overpotential Test Set (Hipot)
and
- AC Overpotential Test Set (Hipot) or
- DC Overpotential Test Set (Hipot) or
- Power Factor Test Set or
- Dissipation Factor Test Set
and
- Digital Low Resistance Ohmmeter (DLRO - 10 amp unit is sufficient.) or
- DC Current Source and a Millivoltmeter
and
- Digital Low Resistance Ohmmeter (DLRO) or
- DC Current Source and a Millivoltmeter
- AC/DC control power source
Not all of these test devices are necessary for each individual standard.
Megohmeters, hipot sets, power factor test sets, and dissipation factor test sets are all dedicated to the testing of insulation integrity.
Digital Low Resistance Ohmmeters (DLRO), and DC current source with mVmeter are instruments for determining the level of resistance in a circuit. This could be a wired circuit or a bussed circuit but in any case a current carrying path. Buss joints and wire or cable connecting points are very sensitive to proper pressure or torque and improper tightness can result in heat build up which can translate into loosening of that connection over time.
Control power sources are used to operate electrically actuated subassemblies such as charge motors, closing coils, trip coils, auxillary relays, digital displays and more.
The recondition evaluation section follows with step-by-step inspection points in logical order to assure all areas are subject to visual observation.
IV. Reconditioning
The next section of the medium voltage circuit breakers & starters standards takes a technician through the "as found" testing steps which includes but is not limited to Insulation Resistance, contact resistance, control device operations. The standard guides the technician through the a number of evaluations, including: overall condition of the various means of isolating current carrying from non current carrying areas of the system; proper level of conductivity through both main power and control power current carrying paths; proper operation of control devices and smoothness of operation of mechanical elements such as pivots, bearings, levers, springs; debris, corrosion or indications of deterioration. Once all tests and inspections are preformed, notes are to be entered into the Recondition Evaluation form.
The visual inspection along with the as-found testing helps determine the actual recondition procedure. The reconditioning procedure specifies disassembly and cleaning of all parts and subassemblies, replacement of parts where necessary, tightening or adjusting where necessary.
Assembly of the reconditioned components and subassemblies is followed by final inspection and testing. As with all testing, inspection, and reconditioning operations, final inspection and test results are recorded onto the Evaluation and Test forms included with the standard. If a PEARL certified technician follows the reconditioning standard, the medium voltage circuit breakers & starters assembly is eligible for a Blue PEARL Reconditioned Quality Seal.
Links to the full reconditioning standards for medium voltage circuit breakers and starters:
Link to the full Standard Number 2210
Medium Voltage Air Circuit Breakers
Link to the full Standard Number 2220
Medium Voltage Vacuum Circuit Breakers
Link to the full Standard Number 2230
SF6 Circuit Breakers
Link to the full Standard Number 2250
Medium Voltage Air Contactors
Link to the full Standard Number 2230
Medium Voltage Vacuum Contactors
Link to view and/or download PEARL's 137 reconditioning standards for electrical equipment.
