troubleshooting

How do I know my electrical system has issues?

Assessing the state of an electrical system goes far beyond simply on/off or works/doesn't-work. If you've ever experienced flickering lights because something else in the house was turned on, then you've experienced the subtle and intricate relationship that exists between every component making up a power system.  

While the lifespan of a light bulb rarely comes up as an issue, crucial and expensive equipment your business relies on can be prey to the same issues and you wouldn't necessarily know it.  

Below is a partial list of some of the symptoms to look for when determining if one has an issue with their electrical system and power quality.  

Utility / Billing

  • Complaints of excessive harmonic production
  • High power factor penalty charges
  • Unexpected changes in power factor
  • Complaints of causing system voltage disturbances
  • Excessive utility attention paid to your substation
  • Excessive outages
  • Excessive voltage sags or swells causing plant-wide disturbances
  • Frequent capacitor switching
  • Complaints of excessive LTC or regulator tapping
  • Unexpected energy charges

Lighting

  • Excessive light flicker or intensity fluctuation
  • Lighting failures
  • Lighting controller malfunctions or failures

Transformers

  • Winding overheating
  • Core overheating
  • General overheating
  • Excessive vibration or noise
  • Failures
  • High levels of combustable or carbon based gases
  • Overheated neutral
  • Excessive internal fuse blowing

Capacitor Banks

  • Abnormal number of blown capacitor units
  • Excessive vibration or noise, high frequency ringing
  • Overheated buswork or cables
  • Unusual bank tripping by upstream protection

Harmonic Filters

  • Reactor overheating
  • Abnormal number of blown capacitor units
  • Excessive vibration or noise, high frequency ringing
  • Resistor overheating
  • Unusual filters tripping by upstream protection

Main Bus

  • Abnormally high or low voltage
  • Abnormal voltage fluctuations
  • Excessive buswork noise
  • Unusual power fluctuations
  • Excessive voltage imbalance

Fuses / Breakers / Relays / ATS

  • Abnormal or excessive fuse blowing
  • Abnormal or excessive breaker tripping
  • Nuisance ATS operation
  • Nuisance Relay operation
  • ATS failure to transfer
  • Nuisance Breaker operation
  • Poor synchronization

Overhead Lines

  • Excessive line trips
  • Excessive conductor movement
  • Unexplained flashovers
  • Excessive line corona

Generators

  • Overheating of generator machine
  • Overheating of generator engine
  • Loss of full load capability
  • Loss of engine efficiency
  • Inability to hold frequency
  • Inability to hold voltage
  • Failure to start
  • Failures of machine or engine
  • Excessive bearing failures

Panels

  • Overheated neutral wiring
  • Overheated conductors
  • Overheated breakers
  • Nuisance breaker tripping
  • Excessive voltage imbalance

Motors / MCCs / Drives

  • Excessive winding failures
  • Excessive bearing failures
  • General overheating
  • Unusual or intermittent contactor drop outs
  • Contactor failures
  • Overheated breaker
  • Unusual or intermittent breaker trips
  • Excessive breaker failures
  • Excessive drive failures
  • Drive input MOV failures
  • Excessive drive misoperation or shutdown

Cables

  • Excessive cable movement in cable tray
  • Overheated cables
  • Melted external jacket
  • Melted insulation
  • Cut insulation and/or charred arcing at cut

Busway

  • Excessive busway movement
  • Overheated busway
  • Excessive vibration or noise

General Plant Equipment

  • Unexpected shutdowns
  • Printed circuit board failures
  • Excessive PLC failures
  • Excessive industrial PC failures

General Office Conditions

  • Unexpected shutdowns
  • Excessive PC reboots, crashes or lock-ups
  • Excessive PC failures
  • Poor network communication
  • Unexpected loss of data or corrupted files on PCs
  • Unexpected loss of telecommunications

Wind Farm Transformer Failure


The inter-operability of equipment.

Detailed investigation of pad mount transformer (PMT) failures led to discovering wind turbine inverter induced high frequency noise being applied to the low voltage line-to-neutral windings. This was not expected, and significant effort was made to ensure this noise was truly present and not a sympathetic response of the data acquisition hardware to radiated inverter switching noise. Measurements were moved from inside the turbine tower to outside on the direct secondary of the PMT. The key issue with this noise is that these transformers were not of any special design to accommodate the high frequency content, and its creation of high peak voltage stress. As shown in the figure above, peak voltage stress due to the noise exceeded 1.5 per unit of the rated secondary line to neutral voltage (398.37 VLN).

Static Var Compensator Commissioning

The importance of commissioning.

In many cases, sophisticated power equipment is not set to run “as-is” after installation and proper commissioning and troubleshooting can be needed to get equipment operating properly.

Theme parks are constantly in search of new and intense thrill rides, and with this often comes even greater power requirements. In this case study, simulation work determined a ride’s reactive power requirement was too great and necessitated a static var compensator (i.e. real-time var compensation) to keep the ride from creating excessive voltage flicker across the power distribution system. After installation, the equipment was monitored to ensure it was providing the specified vars within the specified time response.

Due to the fast load and unload profile of the ride, the static var needed to operate in an open-loop control mode, matching var for var to create a net unity power factor load. During commissioning it was discovered the response was inadequate and the source inverter modules were producing excessive harmonics. Vendor investigation uncovered a need for significant updates in the controls and logic. Unfortunately, that initial update caused a failure in the static var which blew all fuses on the input. Powerlens™ real-time captured waveforms of the fault allowing the vendor’s engineer to quickly determine the problem’s source and implement an effective solution.

Mysterious Feeder Faults


Don’t stop until you catch the problem in the act.

An oil pumping station utilized a long overhead feeder to transfer prime power generation from diesel generators to a pumping station. This line had a series of mysterious faults and subsequent trips with no apparent cause. To investigate this issue, instrumentation was set to capture faults at one end of the line. After capturing the first fault (see figure above), data was analyzed to determine the fault location on the feeder. That location was inspected and again yielded no conclusion of the cause. After capturing 4 to 5 faults, evaluating the fault location and performing multiple inspections, still no root cause had surfaced.

The next step was visually monitoring locations along the line until another fault occurred. Eventually, it was noted that wasps were building mud nests on the insulators. This mud contamination covered significant insulator creep. It was only a matter of time until this mud nest would flashover on the insulator and be vaporized leaving no evidence of its role in the problem. Since there is no solution that can control the nest building activities of these insects, and any material added to the insulator would compromise its insulating capability, the best and only option was replacing the overhead line with an underground cable.