INTRODUCTION
The enjoyment of opening a new building or starting up a new mechanical or electrical system can be annoying quickly if the system does not work the way manufacturer, integrator or designers intended. One way to help avoid this disappointment and subsequent costly refinements or repairs is Commissioning.
Commissioning helps ensure that the system/s will meet the needs of the owner and occupants. It also verifies that the designed system meets the owners requirements and that construction confirms to the contract documents and the system/s operate as needed.
Commissioning building usually covers air conditioning, electrical, communications, security and fire management system and their controls. It may also include other systems and components, particularly if they are unusual or complex.
Electrical System Commissioning
A. Work included
- Systems and equipment testing and start-up.
- Validation of proper and thorough installation of systems and equipment
- Equipment performance verification.
- Functional testing of electrical systems.
- Documentation of tests, procedures, and installations.
- Coordination of training.
B. Scope
- Systems to be commissioned include the following:
1. Secondary Service Electrical Systems
2. Motor Control Centers
3. Distribution and Branch circuit panel boards
4. Lighting Fixtures and Controls
5. Lightning Protection Equipment and Lightning Protection Systems
6. Equipment Monitoring
7. Fire Alarm Equipment/Fire Alarm Equipment Monitoring System
8. AC motors
9. Grounding Equipment and Building Grounding System
10. Security System
11. Emergency Generators and Distribution System
12. Uninterruptible Power Systems
Along with drawings and equipment manuals, a final commissioning report is also submitted to the owner. A complete commissioning report contains:
- All record of the commissioning procedures
- Testing results
- Deficiency notices and records of the satisfactory corrections of deficiencies.
The following areas are addressed: general commissioning criteria, commissioning plan, documentation requirements, verification procedures system functional performance tests, deferred performance tests, corrective measures, acceptance documentation, post commissioning follow-up procedures and examples of commissioning.
General system testing requirements
The purpose of electric systems commissioning is to increase the reliability of electric power system after installation by identifying problems and providing a set of baseline values for comparison with subsequent routine tests. A procedure should be developed to include a planned approach (road map) of what should be done in order to verify the proper system installation. This procedure is the commissioning plan. Specific areas addressed in a commissioning plan include the verification of the installation of all equipment/components, interface connections between equipment and individual system, and interconnection drawings. The development of this test plan specific to each system and/or component is key to the usefulness of any maintenance program. The plan consists of: a) the schedule of when acceptance and routine tests should be performed; b) test forms to be used to record the outcome of the tests which are retained for comparison with previous and subsequent tests; and c) a listing of the required test devices. Since the results of the commissioning tests become baseline test values to compare with later tests and the results of the routine maintenance tests are compiled to identify any downward trend in performance, it is vital to the maintenance program to have accurate and complete records. To perform the testing, the plan lists all required tests in order of performance and gives a schedule for each test. The work items and schedule depend on many items including the importance and cost of the equipment, consequences of failure, age of equipment, past and future frequency of service, hours of operation, future maintenance availability, environmental conditions, and safety requirements.
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Component testing
Commissioning requirements for the system components are typically provided with the original proposal for the procurement of the equipment. The requirements provided by the equipment manufacturer should be adhered to in addition to the recommended testing herein. Although there are many different components in any electrical system, there are some tests that are common among the equipment. Examples of the common testing procedures include the assembly check, alignment check, grounding verification, insulation resistance tests and polarization index to name a few.
Sufficient time should be allocated to define the inspections required, perform the check, and document the results. A review of the system drawings will show major pieces of equipment. Specific procedures should be developed for each test referencing the equipment to be used, drawings to be followed, and step by step procedures with readings to be recorded and forms for the results.
System commissioning testing
Electrical system commissioning on new projects is critical to ascertain that a system is installed properly and that it will operate as designed. The commissioning of a system encompasses the individual testing of the related components, the verification of the component interconnection against the drawings, and the functional testing of the system as a whole. An understanding of the equipment involved and the modes of operation for a system are essential to the development of the system commissioning plan. A survey of the equipment of the system and listing the equipment in order of importance and startup is the first step in developing the commissioning plan. The schedule of the tests and inspections is dependent on many aspects of the equipment such as its importance and cost, the frequency of service, hours of operation, environmental conditions, accessibility, and safety requirements. The inspection, testing, and startup plan is then developed in conjunction with this schedule with instructions and procedures for the test plan. Problems may arise during the testing of the equipment and system. In order to identify and correct these problems, troubleshooting techniques should be developed. Checking of equipment such as fuses, lights, and breakers for continuity, equipment calibration and settings, and investigating for faulty equipment or connections should be the first troubleshooting steps. For all problems, the equipment and component manuals are consulted for troubleshooting directions.
Equipment Needed in Commissioning
Multi-tester is used to measure the voltage, the resistance or the current of a circuit. It is connected in either parallel or series with the circuit depending on what to measure.
A multimeter can be a hand-held device useful for basic fault finding and field service work or a bench instrument which can measure to a very high degree of accuracy. They can be used to troubleshoot electrical problems in a wide array of industrial and household devices such as batteries, motor controls, appliances, power supplies, and wiring systems.
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| Analog and Digital Multimeter |
Megger is an instrument used to measure the insulation resistance of conductors or wire. It is measured in ohms or meg-ohms. It is connected in parallel with the circuit.
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| Megger |
A megger (or sometimes meggar) is often used as an alternate term for an insulation tester - a circuit tester which puts a very high voltage at a very low current across two conductors to make sure that they are properly insulated. The word is short for megohm-meter
High potential tester is an electronic device used to verify the electrical insulation in a cable, printed circuit board, electric motor, transformer or other wired assembly. A hipot tester is used to perform a high potential test.
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| High potential tester |
Generally a High potential tester consists of:
- A source of high voltage,
- A current meter,
- A switching matrix used to connect the high voltage source and the current meter to all of the contact points in a cable.
In addition to these parts a hipot tester may also have a microcontroller and a display to automate the testing process and display the testing results.
A hipot tester can be very similar to a cable tester and often the two are combined into a single device.
A hipot tester is used to verify the circuits that should be insulated. It is done by applying a high voltage between the circuits and making sure no current flows.
In a typical wired assembly, a hipot test should connect all circuits in common to ground. Then, one by one the tester will disconnect a given circuit from ground and connect that circuit to high voltage. The current that flows is monitored to verify that it is low enough.
Phase sequence tester - is two measurement devices in one unit that provides three functions - phase sequence identification, open phase condition and motor rotation indication. Amprobe's Phase Sequence and Motor Rotation Tester is used to assure proper and safe connection of the electrical equipment on three-phase systems.
Phase sequence testing is crucial for some of the three-phase loads, whenever they need to be connected to the electrical system. Improper connection of three-phase motors may lead to reverse rotation, and as a result it may damage equipment powered by a motor.
Note. In this module, the focus of the commissioning process lies on the following:
- Insulation resistance
- Earth resistance test
- Phase sequence test
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