PPE
Millennium Court
Ellerbeck Way
Stokesley
North Yorkshire
TS9 5JZ
Tel: +44 (0)1642 714661 Fax: +44 (0)1642 714662
Case Study 1: Poor Site Power Factor
The problem:
A motor part manufacture was being charged for excessive reactive power demands from the local
distribution network operator (DNO) due to having a low power factor.
The finding:
A power factor survey identified low power factors on two of the three distribution transformers on site. It was
considered prudent to investigate the levels of harmonic distortion due to the nature of the
load (over 20% non-linear).
The solution:
We recommended the installation of power factor correction equipment to the problem transformers.
Each of the banks was specified as detuned to prevent harmonic problems on site.
The results:
The power factor of each transformer was improved to 0.97 lagging. The overall site power factor was improved to 0.95 lagging. The site electricity billing was reduced by £4,272 per annum. The capital outlay was recovered within an 18 month period.
Case Study 2: High Neutral Current
The problem:
A supermarket distribution warehouse reported a current of over 81 Amps (rms) in it's main earth cable.
The finding:
After further investigation by one of our Power Quality specialists, it was found that
over 600 Amps of 3rd harmonic was flowing in the neutral.
The solution:
We recommended installation of two passive neutral current filters.
The results:
The 3rd harmonic in the neutral reduced from 600 Amps to less than 100 Amps. Voltage flat-topping was substantially reduced. Maximum Voltage Total Harmonic Distortion was reduced from 4.8% to 3.8%. Maximum Current Total Harmonic Distortion was reduced from 28% to 19%. The main earth current was reduced from 81 Amps to 40 Amps.
Case Study 3: G5/4 Compliance
The problem:
A water utility site was being refurbished and, as a result, had to apply for a supply upgrade. Due to a large
number of Variable Speed Drives being added, the local utility company insisted that a G5/4 assessment was performed.
The finding:
A G5/4 compliant study was carried out on the existing site to assess the background distortion levels. A voltage assessment was conducted, adding the new loads to the existing recorded levels of distortion.
The solution:
We recommended the installation of active harmonic filtration to two new motor control centres being
installed as part of the refurbishment.
The results:
A connection agreement was granted for the supply upgade. A post-installation G5/4 study was carried out with the conclusion that G5/4 Stage 2 compliance had been achieved.
The power factor of each transformer was improved to 0.97 lagging.