Third-Party Inspection of Control Panel
An electrical panel is nothing but a load control center. All the electrical actions such as power distribution, power transmission, and power system protection are performed by using the electrical panels only. The electrical scheme/wiring diagram will be established using electrical panels & Electrical panels are the practical installation of the electrical wiring diagram. It consists of the trip circuit, closing circuits, bus bars, cables, MCCBs, MCBs, MPCBs, NO & NCs, etc. Electrical panels are ensuring the safe power distribution to the load. Electrical panels are manufactured of rolled steel and well-shaped either rectangle or square.
Control Panel is classified into different types as per application.
- Control Panel
- PCC – The power control center
- MCC – Motor Control Center
- MLDB – Main Lighting Distribution board
Control Panel: The Control Panel consists of circuit control elements such as protecting relays, meters, alarm circuits, PLCs, SMPS, Small power sources, etc. These panels will be placed near the maintenance operator’s place or the operator will be monitored by the control panel.
PCC panel: PCC is a short form for Power Control Center. This is the heart of the control circuit. The output of the generators or transformers is given to PCC. The major power circuit equipment will be installed in this panel. It consists of circuit breakers, Busbar, PTs (Potential Transformer), CTs (Current Transformer), insulators, etc. Major protection circuits will be installed in this panel to protect transformers, Motors, Generators, etc. The Output Power from the PCC panel will be distributed to MCC panels via feeders.
MCC Panel: MCC is a short form for the Motor control center. It consists of Feeders. And feeder contains a motor starter, SFU, MCB, MCCB, MPCBs, Control transformer, meters, etc. Once you open the door of MCC panel doors you can access all the circuit breakers or fuses. Usually one of these panels feeds all the circuits in the power plant or other electrical applications but there may be a situation where there is another “sub-panel” such as a welding distribution board or lighting distribution board serving a dedicated area.
MLDB- Main Lighting Distribution Board: Distributes power to the lighting circuits.
The common reasons for Electrical Control Panel Failure:
Tripped breakers or blown fuses: Depending on how an electrical circuit is protected, an overload will cause a breaker trip or a blown fuse. If your electrical system is acting funky, check for tripped breakers or blown fuses first. These circuits are isolated so the control system could appear to be functioning normally but part of the system’s process won’t function.
Power Spikes and Surges: Unexpected electrical events from the power company or the elements can damage panels, leading to lost controller programs, faulted VFDs, and damaged electronics. Sadly, much of the damage can be instantaneous.
Cut or ground wires in the conduit systems: Electrical contractors will often use Electrical Metallic Tubing (EMT) conduit or flexible conduit in places where they are stepped on or damaged by contact. When damaged, the conduit can separate from the wires and cut into them causing them to ground on the conduit or cut in half. This can cause tripped breakers, blown fuses, shorted power supplies, and unexpected machine operations that could seriously injure personnel. To prevent this, perform routine inspections of conduit systems.
Tripped overloads on power circuits: Most motor starters are protected using an overload set to the Full Load Current of the motor. If the electrical load on the motor is excessive or the motor windings are short, the current will exceed the motors rated full load amps causing a trip. In most cases, the overload is wired using the neutral so when troubleshooting, measure from the neutral on the contractor and not the ground. Additionally, most overloads have an indicator on the front that alerts you when it’s tripped. Correct the problem and then use the overloads reset button to reset the device.
Loose or disconnected wires: Many manufacturers use screw terminals to fasten their electrical wires. These types of terminals are susceptible to vibration that can cause loosening over time, eventually leading to an open circuit that is difficult to troubleshoot due to the appearance of a connected terminal. Regularly inspecting your screw terminals for tight connections will prevent this. Alternatively, many companies, including Innovative IDM, offer spring clamp terminal technology that won’t loosen and rarely has to be checked.
Carbon build-up on relay or contactor contacts: Carbon naturally accumulates on contacts that arc when opening and closing. Over time, carbon will cover the contact, blocking conductance through the contactor or relay. An easy way to check is to energize the relay and use a voltmeter to measure across the contacts to verify the contacts are conducting. If the voltage is read across the contacts, you’re OK. If not, there’s your problem: Use contact cleaner to remove the carbon or replace the component is beyond cleaning.
Manufacturing Defects of Electrical Control Panel:
- Fabrication defects
- Paint / Coating Defects
- Loose Connections
- The positioning of filters and power supplies
- Partition confines space
- Equipment Layout in the panel
- “Tightness” to interference
- Polluted Wires
- Protective Shielding
- Interference, or disturbances of all frequencies
- Loose Assembly
Control Panel specifications are key to matching load and operating conditions with electrical protection and efficiency. Nameplate provides important information relevant to its selection and application. Front panels and faceplates may include metal or plastic substrates, depending on the application specifications, and can be mounted with studs, adhesives, or fasteners. Digital or screen-printed graphics provide visual guidance for operators and incorporate the labeling of operator devices to ensure usability. Therefore, faceplates must have the durability necessary to remain readable for the life of the asset.
All control panel inspection and testing are done against the approved drawings, purchase order specifications, purchasers or company standards, and within the practices and rules of the country, state, or province, and any government decrees, laws, ordinances, or regulations as may apply.
The applicable codes and specifications for a control panel that is under the construction process are:
- Design Code and Standard
- Purchase order specification
- Purchaser’s standards
- Approved Drawings
Applicable IS Standards for Control Panel
The applicable codes and standards may be based on any international standards.
This content is general and can be useful for all recognized standards. Ref. some of IS Standards as:
- IS 8623-1 (1993): Low-Voltage Switchgear and Control gear.
- IS 8623-2: Factory assemblies of switchgear and control gear for voltages up to and including 1000 V AC and 1200 V DC: Particular requirements for busbar trunking system (busways).
- IS 5133(Part-1) – Boxes for enclosure of electrical accessories: Steel and cast iron boxes.
- IS 4615 – Switch socket outlets (non-interlocking type).
- IS 4160 – Interlocking switch socket outlet.
- IS:1293 – Plugs and socket outlets of rated voltage up to and including 250 volts and rated current up to and including 16 amperes.
- IS:10118(Part-1) – Code of practice for selection, installation, and maintenance of switchgear and control gear: General
- IS: 10118(Part-2) – Code of practice for selection, installation, and maintenance of switchgear and control gear
- IS 10118(Part-3) – Code of practice for selection, installation, and maintenance of switchgear and control gear: Installation.
- IS 10118(Part-4) – Code of practice for selection, installation, and maintenance of switchgear and control gear: Maintenance.
- IS:4237 – General requirements for switchgear and control gear for voltages not exceeding 1000 V AC or 1200 V DC
- IS 6875(Part-1) – Control switches (switching devices for control and auxiliary circuits including contractor relays) for voltages up to and including 1000 V AC and 1200 DC: General requirements and tests.
- IS:4064(Part-1) – Air break switches, air break disconnectors, air brake switch disconnectors, and fuse combination units for voltages not exceeding 1000 V AC or 1200 DC: General requirements.
Third-Party Inspection Document Review for Control Panel
When Third Party Inspection agency performs the Inspection of the Control Panel, The followings documents are to be checked/verified (But Not Limited)
This are the list of documents that are normally agreed upon to be presented to the inspector:
- Control Panel Purchase Order or Contract
- Control Panel Manufacturer Quality Control Manual
- Control Panel Manufacture Quality Control Plan
- Control Panel Inspection and Test Plan
- Control Panel Data Sheet
- Control Panel Approved Drawings, (arrangements, schematics, wiring, single line)
- Control Panel Material Test Reports
- Control Panel Welding Specification Procedures (WPS) and Procedure Qualification Records(PQR)
- Control Panel Welders Qualifications Reports
- Control Panel Calibration Certificates for Test Equipment
- Control Panel Special Procedures
- Control Panel Special Qualifications
- Control Panel Preparation and Painting Procedure
- Control Panel Preservation, Packing, and Shipping Procedure
- Control Panel Packing List.
A very important aspect is the technical documentation that has to be prepared by the manufacturer of the Control panel which must include the following characteristics:
- rated operational voltage Ue;
- rated voltage Un;
- rated insulation voltage Ui;
- rated impulse withstand voltage Uimp;
- rated conditional short-circuit current Icc ;
- rated current In;
- short-time withstand current Icw;
- rated current for each circuit Inc;
- peak withstand current Ipk;
- nominal frequency fn;
- nominal factors of contemporaneity;
- degree of pollution;
- degree of protection;
- degree of protection to mechanical impact;
- type of installation: internal or external;
- type of installation: stationary or mobile;
- type of use: PEI or PEC;
- special conditions of use.
Third-Party Inspection of Control Panel
During the Third-Party Inspection of Control Panel, the Third-Party Inspection services provider Third Party Inspection Agency – inspector takes into consideration the Followings
The review includes checks on:
- Maker’s name and location
- The certificate number, grade
- Batch Number
- Chemical composition
- Mechanical Properties
- Cast or Heat number (for metal parts)
- Heat treatment condition
- Surface finish (if required)
- Structural observations, notable defects
Ancillary items may be supported by test certification, or by certificates of conformity. It is necessary for the content of the certification to be appropriate to the required scope of the items.
It is also necessary to check material identification with the control panel drawing datasheet, material list, and other specifications as appropriate.
When the third-party inspector carries out the material inspection, then provides the inspection visit report, the report contains the following items:
- Confirmation of satisfactory document review
- Record of the endorsement of certification reviewed/witnessed
- Record all non-conformities
- Record of any tests witnessed and the result
Construction of Control Panel:
- Checking of outline dimensions, interface dimensions, bus bar dimensions, Clearances, and other specified dimensions
- Marking/ Name Plate
- Tightness/torque of terminals
- Degree of Protection
- Any Manufacturing / Assembly Defects
- All instruments, compartments, control switches, etc. are correctly rated and are correctly located, with specified labeling.
Insulation Resistance Test
Insulation resistance is measured between control circuits and the earth (with sensitive devices excluded) with a 500V Megger. Similarly, insulation resistance is measured in all applicable permutations for any power circuits, if these are included within the control system, with a Megger selected to the voltage calculated appropriate to the applicable specification. The test result depends on the circuit but would not be acceptable if it is less than 2 Megohms.
Withstand Voltage Test / Dielectric Test
A power frequency voltage of 1.5 kV is applied between control circuits and the earth for 1 minute. Similarly, power frequency voltage, calculated appropriately to the applicable specification, is applied to all applicable permutations for power circuits for 1 minute.
The test would be acceptable if no flashover or puncture occurs during the test.
Control circuitry is functionally tested and circuits are proven by appropriate tests. The test result would be acceptable if meet approved schematic diagrams (including appropriate, recorded, “as built” alterations) and project philosophy.
- Relay Test – As a main protection element, the testing of the relay performance and settings is always included in any panel test; the different relay types, relay generation, and specific protection functions will define the suitable relay test set.
- Secondary Injection Test – The electrical panel test also involves checking all the wiring and signals to the relays and instruments, for the proper operation of the protection logic and the measuring reliability. The continuity and operation of the protection and control circuits during the panel test are a key factors in security. Point-to-point checks of the wiring through secondary injection are usual in the panel test procedures, and any of the mentioned secondary injection test sets can be used as current or voltage sources to perform verification of the different control, signaling, and tripping circuits, through the generation of nominal and fault values.
- Scheme Test – For verification of the tripping scheme, the panel test procedure may include the simulation of protection sequences, for which the easy-to-program state sequencer included in Mentor 12 is an invaluable tool that does not require the use of a PC, and can also include GPS timed sequences. The ROOTS (Relay Object‐Oriented Test System) is a powerful automation software, which includes pre-programmed scheme tests, oriented to specific protection modules, such as reclose functions, circuit breaker failure, fuse failure, etc.
- Primary injection Test – Elements such as MCBs and MMCBs may require in the panel test of higher currents than the range provided by the secondary injection test sets, for which any of the LET range or any of the Raptor configurations are suitable as a high current source for magnetic and short circuit trip tests; likewise, the same equipment can be used for the whole panel performance through a primary injection test; the panel test may include the heating verification under long-term current conditions, for which the Raptor is very suitable because of its stability throughout the injection time; now the optional HV unit provides also the capacity to perform dielectric strength checks up to 2000 V, to those elements that must keep insulation integrity in the panel test.
- Contact Resistance Test – Another typical task in the panel test is to perform contact resistance tests in all bus joints and critical connections, to avoid higher resistance paths and dangerous hot spots. SMC offers different micro ohmmeters for this purpose, but we highlight our new PRIME 600, which provides pure DC, which becomes important when checking a whole bus bar, and the resistance measurement could be affected by the nature of the DC injected.
- Polarity Test – A reversed polarity may cause the protection not to work or be unstable; the PME-20-PH can be used for polarity testing in combination with any of the secondary injection test units; the Raptor Polarity Tester provides a more straightforward and efficient checking of the polarity in the panel test, with a special waveform generated by the Raptor at the beginning of the circuit, which is comfortably traced downstream by the small handheld Polarity tester.
Mechanical Operation Test
The following mechanisms are checked for operation:
- Interlocking systems
- Drawing mechanisms
- Opening and shutting mechanisms
The test would be acceptable if all the mechanisms work correctly.
Painting & Coating Inspection
Surface preparation for painting is checked for the following points, according to specification by a third-party inspector:
- Cleaning Method (Blast or scraping and wire brushing)
- Preparation Grades
- Freedom from weld spatter, blowholes, and other defects
- Dry film thickness is checked according to the specification
It is necessary for the surface condition to be free from pinholes, run damage, and other discontinuity.
Packing, Marking, and Shipping
The following points are checked by the third-party inspector for packing inspection:
Verify that the packing materials conform to specifications and accepted practices for the mode of transport
- Verify protection against humidity, abrasion, distortion, and other damage.
- Verify shipping marks to marking instructions and record.
- Verify handling marks.
Third-Party Inspection Agency in India
We are a leading Third-Party Inspection Agency in India providing Third Party Inspection services in most of the industrial sectors – Mechanical, Electrical, Engineering, Handicraft, Food Products, FBO, Construction, Infrastructure, Pre-shipment inspections, etc many more Industrial sectors.
We have a Highly Experience Team of Engineers team with us – who have vast Experience in the Inspection of Electrical products including – Control Panel.
The Control Panel has wide applications in Industrial and Domestic Applications. So, the importance of its Quality and Reliability must be checked by Manufactures before delivery of the product, or get it to be Inspected by Third Party Inspection Agency to ensure the same.