MPAC Power Quality Analysis

Since 2005 MPAC Ltd. have been carrying out predictive maintenance and condition monitoring services for customers in all industries across the county, we have developed a strong understanding of the various technologies used in industrial and commercial predictive maintenance and have invested in state of the art equipment to allow us to carry out inspections on electrical and mechanical systems for our customers.

MPAC Ltd. can offer power quality analysis services to customers for condition monitoring, fault finding and root cause analysis.

Our power quality analysis equipment can be connected to a single piece of equipment, a room or production area, a building floor, a building on a site or the complete site from the main incomer.

Our power surveys analyse the electrical power on single phase or three phase systems over a period of time (often 1 week or more) and are tailored to focus on the particular area of concern, such as:

 

  • Electrical load profiling:

All aspects of the electrical supply can be datalogged and analysed for various purposes including

evaluating capacity of the system

investigating the need for increasing / decreasing the supply from the electricity provider

energy usage surveys etc.

We can set up our logging equipment to record any conceivable parameter of the electrical system depending on the purpose of the investigation. Typical values recorded are as follows:

Voltage (V)

Current (A)

Power (kw, kva, kvar)

Energy (kwh, kvah, kvarh)

Power factor (Cos θ)

The typical recording period for this type of survey is 1 week but this can be customised to suit customer requirements.

 

  • Supply efficiency and cost reduction opportunities:

Similar to load profiling but with the view to identifying where electricity consumption can be reduced or eliminated by improving practices and modernising / upgrading equipment. These upgrades can sometimes be grant aided by state bodies and can offer a very quick return on investment (ROI) as well as long term savings an cost reductions.

 

  • Dips, swells and voltage disturbances:

A voltage dip by definition is a decrease in the RMS voltage below the nominal voltage. The decrease lasts from half a cycle to several seconds.

A voltage swell by definition is an increase in the RMS voltage above the nominal voltage. The increase lasts from half a cycle to several seconds.

Faults on the electrical power distribution system cause these types of disturbances sometime these faults occur within your facility sometimes the root cause is in a neighbouring facility or is the result of a poorly planned or overloaded electrical network supplying your building or industrial park.

 

Causes of voltage dips within your facility can include:

Short circuits on cables, switchgear or equipment,

Switching on of large loads,

Inefficient or obsolete methods of starting electrical loads,

Damaged loose or improper connections at or after the main incomer,

Unbalanced network within the facility,

 

Causes of voltage dips from outside your facility can include:

Site location remote to electrical grid,

Site is a long distance from the supplying transformer (LV customers in industrial areas),

Neighbouring facilities switching heavy loads,

Overloaded or poor MV / LV network in the area,

Damaged loose or improper connections before the main incomer,

Line faults / transformer faults,

Electrical faults in neighbouring facilities,

 

Causes of voltage swells within your facility can include:

Switching off large loads,

Capacitor banks energizing,

Transfer of loads from one power source to another (MV sites)

 

Causes of voltage swells from outside your facility can include:

Neighbouring facilities switching off large loads,

Transfer of loads from one power source to another (load shedding on the national grid)

Line faults / transformer faults,

Voltage levels being increased by the supply company at certain times in anticipation of expected demand,

A change in voltage causes a decrease or an increase in the amount of energy supplied to components in an electrical power system. A decrease in energy during a voltage dip can cause equipment to reset or shut down and cause mechanical devices, such as motors, to stall or overheat. An increase in voltage during a voltage swell can cause immediate or long-term breakdown of components because of overheating and component failure.

Common symptoms of voltage disturbances reported to us from customers include

Production rates fluctuates

Equipment does not operate correctly

Dimming of lighting systems

Variable speed drives shut down unexpectedly, stopping the production process

Relays and contactors drop out unexpectedly, stopping the production process

Robots, CNC machines and other sensitive equipment shutdown unexpectedly, stopping the production process

High number of component failures including motors burning out, control cards failing, general electrical related breakdowns are frequent within production equipment.

 

  • Power factor correction:

Power factor is the ratio between the kW and the kVA (actual power vs apparent power). Simply put, it is a measure of how efficiently the load current is being converted into useful work or how efficiently your electrical system in the facility is working.

In any real world installation, we never see 100% efficiency because most electrical loads such as electric motors, processing machines, lighting etc. are what we call “inductive loads” which in turn causes the current in the supply to lag the voltage. The resulting lag is called Power Factor. Power factor is measures from 0.00 – 1.00 (a power factor of 1 is not desirable for other reasons but 0.98 – 0.99 is taken as 100% efficiency).

When the power factor falls below a set figure, the electricity supply company charges a premium on the kW units being consumed in terms of penalties to the bill. These penalties can be seen in the breakdown of charges section of the electrical bill and will be charges denominated as wattless units / wattless power or wattless charges

The reason the electrical supply company charges penalties for excess wattless current is that they have to generate and transmit electrical power to an inefficient facility that ultimately does no work for the end user only causes problems within the facility.

So to summarise: wattless power is power that has to be generated and transmitted but does no work.

The solution is quite simple, once we ascertain the actual efficiency of the system we can correctly size and build a power factor correction panel that will be connected in parallel with the main electrical supply, this power factor correction unit comprises of banks of capacitors which are switched into service in steps to counteract the inductance at any given moment.

In electrical terms Capacitance is the polar opposite to inductance and adding the same value of capacitance to the network as inductance will ensure the facility works as close to 100% efficiency for the given load as is practically possible. The capacitance is switched in and out in steps because in any installation the load is rarely constant (motors start and stop, machines turn on and off as do lighting circuits etc.) therefore the capacitance needed at any given moment is proportional to the load at that moment.

 

Note: When we talk about improving efficiency with regard to power factor this does nothing to improve the efficiency of your equipment, it only improves the efficiency of how the installed equipment uses power. For machine efficiency improvements see our section on energy usage reduction.

 

  • On site investigation:

Investigation of problems requiring several recordings at one or different locations, e.g. investigating trips on motor starts, standby generator / UPS performance tests, fault finding of electrical anomalies, equipment energy usage data gathering.

 

  • Fault Investigation:

Investigation and analysis of electrical faults and failures including intermittent faults and root cause analysis of faults failures and electrical associated damage. For identification and analysis of system faults typically a 1 week logging period is adequate for fault investigation, capturing data on what is happening on the electrical network followed up with a 1 day on-site deeper analysis where necessary. Again custom logging and onsite investigation can be scheduled where necessary.

 

  • Harmonics:

Harmonics is a broadly used term to describe electrical distortion, Harmonic related issues are prominent in installations where loads are supplied through semiconductor type devices and can cause a variety of problems that are sometimes difficult to attribute and eliminate. Loads drawing their current through semiconductors have a non-linear characteristic and are primarily responsible for generating the harmonic distortion that is so damaging to supplies, equipment and sub-components. In a commercial or industrial context there are non-linear loads all around us.

Switch-mode power supplies, PCs, monitors, photo-copiers, fax machines, high-frequency lighting, Variable-Speed Drives, Uninterruptable Power Supplies, 3 phase rectifiers are but a few.

Harmonic Current causes overheating of conductors and their insulation, overheated transformers and increased losses, overloaded Neutral conductors, excess Neutral to Earth potential, overheating of capacitors and, ultimately, premature component failure. Additionally, exporting excessive harmonic distortion to the supply networks can cause energy costs to be increased through penalties from the electricity provider.

Harmonic Voltage causes linear loads to draw non-linear current (resulting in current distortion effects), torque pulsation in motors, capacitor dielectric failure, insulation breakdown, PC monitor and power supply failure, electronic lighting failure, malfunction of sensitive electronic equipment and, again, excessive distortion in distribution supply networks.

Reports can be produced for electricity supply companies to demonstrate compliance with national standards.