Frequently Asked Questions...

In order to provide faster technical help, we have tried to concisely answer some of the more common frequently asked questions.

Q1 Can I make changes to relay parameters online, i.e. while the motor is running or the breaker is closed?

Answer: Grant from customer services says you can. All parameters are stored in a separate part of the memory and once a setting is changed it is stored at the new value. For some settings changes (i.e changing a threshold level) this could result in a trip occurring if the new threshold level is already in a breached condition. It is often best to change settings offline in most circumstances.

Q2 Is there a way to clear all of the programmed settings and start again? 

Answer: The relay can be 'defaulted' i.e factory setting restored by holding down certain keys whilst the unit is powered. A message 'Please Wait'... 'Defaulting Settings' will appear on screen.

  • For those units with graphical displays and 2 menu buttons either side of it, holding down both of the left hand buttons and the bottom right button together causes the unit to 'default' on power-up.
  • For Microvision, hold down all three of the top keys
  • For the 3000 and the N11 retrofits, hold down all three keys starting from the left.

Q3 Do I need to have the programming software to change settings?

Answer: No, Vision Control is a useful tool for programming the relay parameters and for printing or saving a secure copy of the settings. Relays can also be quickly and easily programmed via the front keypad and LCD or via the smart card (if activated).

Phil, May2010

Q4 What Current Transformers would I normally use to connect to P&B relays?

Answer: Normally we would suggest 2.5VA 5p10 for Motor Protection and 5p or 10p20 for Feeder Protection. For Core Balance CTs, (CBCT) used for motor earth fault we recommend 1VA class1/5p3 CTs.

The CT burden of the relay is very low >0.01VA so VAs less than 2.5VA can be used although 2.5VA are more widely available.

The CT secondary ratings are normally specified as either 1A or 5A during the relay order. We can supply ratings at 2A, 10A and 15A to facilitate the direct connection of 380-415V LV motors terminals without the use of interposing ring type CT's.

Q5 Do I always need a swamping resistor, what is it and what should its resistance be?

Answer: Phil York says NO.  A swamping resistor is used to eliminate the possibility of spurious earth fault occurring in residually connected earth fault measurement. On a motor start, the inrush current can cause a false earth to flow through the earth fault element of the relay. A swamping or stabilising resistor can be fitted to avoid 'spill current' flowing during a start, if a genuine earth fault exists the protection relay will operate.

As standard we would offer a 11ohm 30watt variable resistor for a 5A relay and a 370ohm resistor for a 1A relay. If the motor details, CT details and earth fault settings are known we can calculate the most appropriate setting for the resistor.

Q6 If I need to return a relay to P&B, how do I go about it?

Answer: For any non UK customer, relays should be returned under Inward Processing Relief (IPR) to avoid inbound and outbound duty. Your nominated courier should be able to help and advise you.

Relays can be returned to us if marked for the Attention of the Repairs Department. Currently we do not operate a returned material authorisation, however we should always be informed and made aware of all incoming returns prior to despatch in order to make the necessary arrangements.

Any product being returned should include a full description of the problem along with addressee contact details.

If a product is being returned within its guarantee period then we will accept liability for the returning freight costs (i.e leaving the UK) excluding local duties and taxes. If a unit is outside of the guarantee period we would expect the customer to arrange for return collection to their cost.

Contact for further information or phone Caroline Coward on 0044(0)161 230 6363

Q7 What is your standard delivery time?

Answer: Our standard quoted delivery is 4-6weeks. In instances of a requirement for large quantities of relays we would normally negotiate partial or split shipments to allow batched delivery.

For small quantities or for a spare unit required in an emergency (for example) we would aim to despatch more quickly at no extra cost. Carriage costs may of course increase as a result.

Q8 Can I use a single phase kit to test the relay or do I require 3ph equipment?

Answer:  Richard Anstey our Chief of Test says yes.  A single phase kit can be used to test the majority of relay functions. The CT inputs can be wired in a serial fashion so that the single phase supply can be 'seen' on all phases. In some instances though (particularly if primary injecting through ring type CTs with a residual earth fault) then the resultant current summation will 'flow' into the EF element, if a stab resistor is present this may cause damage to the resistor. With three phase equipment the resultant EF current (in a balanced system - magnitude and angle) would be zero.

If you would like to ask a question or suggest an FAQ, please use the contact us page