Publications

This guide sets out recommended planning, design, and installation practices which should be followed when it is desired to install neutral earthing resistors/reactors (NERs) in power systems rated at voltages not more than 20.6kV phase to earth, to limit the flow of current during a fault between phase and earth. This guide is focussed on the use of NERs to control the level of induction or earth potential rise (EPR) hazard to telecommunication users, staff and plant. However, the principles apply to the installation of NERs for any purpose.

A comprehensive coverage is given, not only for the use of NERs in new power system installations, but also for the integration or retrofitting of NERs into existing power systems and for the consequential changes required to existing protection arrangements.

The use of NERs in mining and industrial applications is also included. The guide does not attempt to describe all the conditions to be met for systems operating at higher voltages to earth than 20.6kV, because such systems may incorporate plant with graded insulation, or may be designed for less than the basic insulation levels (BIL) needed when using an NER.

The guide includes graphs from IEC 71 - 2 Annex B (with their permission) for determining transient overvoltages due to earth faults on systems with NERs.

The Appendix giving indicative costs for the installation of NERs has been updated, and a new Appendix added on "Results of a 10 Year Study of Earth Faults on a Combined Urban/Rural 33/11kV Substation Equipped with NER".

Issue 3 updates information relating to ‘resonant earthing with residual current’ systems, and includes some details of a recent installation.

This guide sets out the conditions and procedures which should be used for the planning, design, construction, and extension of single wire earth return (SWER) high voltage power lines, operating at 6.35kV above earth, so that any voltages induced on nearby telecommunication lines are not hazardous to telecommunication users, staff or plant, and do not cause excessive noise.

SWER power lines are a special case of power lines, in that they carry fully and CONTINUOUSLY unbalanced currents and voltages (with respect to earth). Consequently, the much lower "continuous" hazard voltage limit (60Vrms) and noise voltage limit (0.5V phosphometrically weighted) apply.

Examples of SWER exposure calculations for determining induced voltage levels on nearby telecommunication circuits are included.

This guide sets out the technical issues and implications for nearby telecommunication network plant of various cable sheath bonding arrangements for high voltage power cables between substations. The impacts of cable sheath bonding on both power earthing system earth potential rise (EPR) and on induction into parallel telecommunication circuits, and the consequential impact on nearby telecommunication plant, are outlined.

A range of cable sheath bonding systems is outlined together with an explanation of the impact of cable sheath bonding on nearby telecommunication installations as well as on the power network. The advantages and disadvantages of cable sheath bonding are described and a process for the calculation of earth potential rise and transferred earth potential rise for earth mats bonded together is included to assist in determining the most appropriate arrangement for specific cases under study.

Guidance is included to assist in determining when more detailed studies or computer modelling is appropriate to reach a conclusion.

This guide is supplied with a companion paper "Fundamentals of Calculation of Earth Potential Rise in the Underground Power Distribution Cable Network" which provides detailed guidance on the use of the symmetrical components method of analysis to calculate EPR and transferred EPR (TEPR) in a power cable network (see separate abstract).

This paper is a companion paper to the NZCCPTS Application Guide for Cable Sheath Bonding.

This paper provides a detailed outline of how to calculate the fault currents and earth potential rise that will result when a high voltage cable between two substations has its sheath bonded to the substation earth mat at each end.

The fundamentals of how to calculate earth potential rise (EPR) in an underground power distribution network are presented in some detail. The objective is to enable engineers with a basic knowledge of power system analysis to further develop their skills and understanding of EPR calculations in a typical distribution network.

The calculation of sequence impedances to model overhead lines and underground cables and calculate the Earth Potential Rise in the cable network, is presented in some detail, to enable a Power Systems Engineer to understand and design cost effective earth systems.

This paper can be treated as a guide or a reference document for calculating the fault currents in a distribution network. Several fault scenarios were modelled. For each model a numerical example outlining all steps required to calculate EPR is also provided.

The equations given in this document can also be used for calculating line and cable series impedance parameters required by PTI's Power System Simulator (PSS/U) and most other load flow and short circuit analysis software packages.

The methods and the models presented in this paper are such that they can be readily applied to practical situations by a Power Systems Engineer using a basic scientific hand calculator.

This guide provides information on the causes and characteristics of power system disturbing current phenomena and presents guidelines for systematically investigating and mitigating cases of reported power noise interference to telecommunication systems.

Descriptions and explanations are included on a range of disturbing current phenomena, which can arise in parts of the power system, and of conditions in which significant interference to the quality and performance of telecommunication systems can result.

Suggestions are included to assist with interpreting observations and measured data to help engineers achieve a clear understanding of the possible causes and sources of noise in the case under investigation, so that the most appropriate mitigation can be pursued.

This guide sets down principles for determining the apportionment of costs between power and telecommunication network operators when cases of EPR hazard, induction hazard or interference to telecommunication networks require investigation and remedial action, and incur expenditure by either or both parties.

The principles are aimed at achieving resolution of issues by agreement, thus avoiding costly litigation.

This brief document (8 pages) provides industry guidelines on the minimum separations that should apply between buried power and telecommunication cables. The standard minimum separations are summarised in a table. Application Rules are also included to explain how to apply these minimum separations, and what exceptions to the minimum separations are permitted.

A discussion paper explaining the reasons behind these minimum separations is included as an Appendix.

This guide provides a broad overview of Power Coordination. It attempts to tie together and put into context all the relevant NZ legislation, NZCCPTS Guides, AS/NZS standards, EEA standards and other relevant international standards, as well as filling in some of the Power Coordination gaps not covered by all these other standards.

The guide describes Power Co-ordination as a process to identify, analyse and, where necessary, mitigate adverse interactions between Power and Telecommunications networks. The adverse interactions covered in this guide include:

• Hazard to humans.
• Damage to telecommunications network plant and telecommunications network customers’ plant.
• Mal-operation, or substandard operation, of telecommunications cable network circuits.
• Corrosion of metallic telecommunications network plant in direct contact with the ground.

As well as providing references to all the relevant NZCCPTS Guides, AS/NZS standards, EEA standards and other relevant international standards, this guide also includes the following Power Coordination details:

• Description of the power, telecommunications and rail networks in New Zealand.
• Description of the mechanisms of adverse interactions, including details of:
  1. Assumed minimum insulation levels of different telecommunications network cable types.
  2. Typical minimum insulation levels of customer’s mains-powered telecommunications equipment.
• Power Coordination issues with aerial and buried fibre optic cables.
• Power Coordination expertise required.
• Methods of determining impressed EPR and induced voltage levels.
• The need for noise interference issues to be handled in a ‘reactive’ rather than ‘predictive’ manner.
• Relevant planned changes to the Chorus cable network, that will affect its future exposure to Power Coordination hazard and noise.
• Summary of relevant Power Coordination legislation.
• Use of Risk Assessments to demonstrate compliance with the relevant Electricity (Safety) Regulation on Power Coordination hazards.
• Power Industry mitigation options.
• Telecommunications Industry mitigation options.
• Detailed Power Coordination reference list.

This guide will be updated from time to time to reflect progress and advancement of current legislation, codes of practice, international standards and other industry documentation.

This guide is currently available from this website as a free PDF download.

For the control of hazard to telecommunications users, staff and plant arising from Earth Potential Rise during Earth Faults in the Power High Voltage Network.

Note – This Handbook is not a stand-alone document, and instead needs to be read in conjunction with the AS/NZS 3835 family of Earth Potential Rise standards.

In 1989, NZCCPTS published the NZCCPTS Earth Potential Rise Application Guide. The guide set out the agreed conditions and approved procedures which should be used for the planning, design and co-ordination of Power and Telecommunication Systems, so as to control the level of EPR hazard to Telecommunication Users, Staff and Plant within acceptable limits.

This guide has subsequently been superseded by the below AS/NZS 3835:2006 ‘Earth Potential Rise – Protection of telecommunications network users, personnel and plant’ family of standards:

Code of Practice	AS/NZS 3835.1:2006
Application Guide	AS/NZS 3835.2:2006
Worked Examples (handbook)	HB 219:2006

However, there were a few parts in the NZCCPTS Earth Potential Rise Application Guide (primarily the Appendices) that are useful knowledge that is not covered in the above AS/NZS 3835 family of standards. To ensure these are not lost, they have been retained in this NZCCPTS Earth Potential Rise Supplementary Handbook.

As such, this NZCCPTS Earth Potential Rise Supplementary Handbook is not a stand- alone document, and instead needs to be read in conjunction with the above AS/NZS 3835 family of standards.