Harmonic Site Surveys – The Process
To correctly ascertain your requirements a site survey to establish the present levels of Harmonic distortion needs to be carried out. This is how it works:
Assessment of your site conditions
To conduct a Harmonic survey it is necessary to establish the present site conditions. This is to include investigation of the supply transformers, establishment of the Point of Common Coupling (PCC), assessment of the single line distribution including pertinent ancillary equipment such as Power factor equipment on site and the method of connection on the monitoring equipment.
Monitoring Equipment Connection
We go to site and connect the Monitoring Equipment, this is hooked up for one week to record site conditions. This gives us the data to produce a comprehensive report.
This detailed report will include all information required under G5/4. Our proprietary software will be used to interpret current site results and predicted harmonic levels and confirm compliance with current legislation.
We offer a new service ~ Healthcheck which gives you an invaluable snapshot of site conditions and current harmonic conditions. This may avoid the cost of a full blown 7day/week survey.
For more information or to book your survey, please use the Quick Enquiry button at the stop of the page or call us on 024 7655 3303
Why carry out a Harmonic Survey?
High harmonic currents and high harmonic voltage distortion can be the cause of the following problems, often causing disruption to your business:
- Overheating of conductors
- Insulation failure
- Nuisance tripping of circuit breakers
- Nuisance rupturing of fuses
- Additional significant voltage distortion of networks run from generators
- Overheating and possible resonance on networks using capacitors
- Overloaded neutral
- Neutral earth potential (generally due to single phase harmonic loads)
- PC/TV monitor stroboscopic effects
- Malfunction of microprocessor based equipment
- Causes linear devices to draw non linear current (ie- motors)
- Torque pulsations in motors
- Flicker in lighting
- Capacitor dielectric failure
- Insulation breakdown
- PC/TV monitor and power supply failure
- Electronic lighting failure
Both single and three phase non-linear loads draw harmonic currents. For both controlled and uncontrolled rectifiers the dominant harmonic is generally denoted by n-1, where n is the number of rectifying devices, ie a single phase 4 diode rectifier gives a dominant 3rd. harmonic, and a three
phase 6 diode rectifier gives a dominant 5th, harmonic.
Voltage distortion propagates throughout the entire distribution network, and must be regulated by the distributor to avoid the damaging effects.
The magnitude of the distortion is dependent on the current and the network impedance, and the lower the network impedance (higher fault level), the lower the resultant voltage distortion. The levels of acceptable distortion are laid down in a number of standards including EN 50160, and IEC 61000 series.
In theory a current will flow to the lowest impedance, hence it would be expected that harmonic current flow would be up through the increasing voltage levels of the network, however, if there are any resonant components in a network at lower voltage level, such as power factor correction, there can be a flow in this direction.
Limits for Harmonic Voltage & Current
In the UK the network operators are governed by statutory instruments which specify the levels of
service and network power quality and forms part of their license agreement. Part of the power quality requirements are incorporated in an installation standard known as the Energy Networks Association Engineering Recommendation G5/4-1 – Planning levels for harmonic voltage distortion and connection of non-linear equipment to transmission systems and distribution networks in the UK.
This gives a number of Stages that can be applied to connections for consumers, and a guide to its application is available from www.gambica.org.uk.
Visit our ABB Power Quality Products page and take a look at the Filter solutions we offer.
Please call us to discuss your own site requirement. We have many years experience providing a Harmonic Solution for you to meet current legislation.
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