EEA Disclaimer: The Electricity Engineers’ Association of New Zealand accept no liability for loss or damage related to information contained within these publication. All practicable steps were taken prior to publication by the NZCCPRS to ensure the accuracy of the content within. The authors offer no warranty, guarantee, or remedy in the event errors, or omissions, are found after publication.
NZCCPRS Disclaimer: “The information contained in these booklets has been compiled by the NZCCPTS for the use of its members from sources believed to be reliable, but neither the NZCCPTS nor any of the contributors to these guide (whether or not employed by NZCCPTS) undertake any responsibility for any mis-statement of information in the booklet, and readers should rely on their own judgement or, if in doubt, seek expert advice on the application of the guidelines to work being carried out.”
CABLE SEPARATIONS GUIDE 180121: Industry guidelines on the minimum separations that should apply between buried power and telecommunication cables
CABLE SHEATH BONDING – FULL VERSION (PUBLISHED VERSION) 180121: Guide for the control of earth potential rise and for the limitation of hazardous induction into telecommunication circuits
COMPANION DOCUMENT FOR THE NZCCPTS CABLE SHEATH BONDING GUIDE: Fundamentals of Calculation of Earth Potential Rise in the Underground Power Distribution Cable Network (by Ashok Parsotam) (1997)
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.
COST APPORTIONING GUIDE 180121: 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
EPR SUPPLEMENTARY HANDBOOK 180121: When the new standard AS/NZS 3835.1:2006 ‘Earth potential rise—Protection of telecommunications network users, personnel and plant’ standard was published, this effectively superseded large parts of the original NZCCPTS 2002 EPR Application Guide. However the original NZCCPTS 2002 EPR Application Guide included some useful sections not included in AS/NZS 3835:2006.
These were saved into this new NZCCPTS EPR Supplementary Handbook. These are:
Transient EPR Voltage at the Onset of an Earth Fault: Appendices
- A Manual Calculation Sheets for Earth Fault Current and EPR
- B Calculation of Earth Resistance using a 2-layer Earth Resistivity Model
- C Measurement of Earth Resistivity
- D Measurement of Earth Resistance
- E Worked Example – 33/11 kV Substation
- F Worked Example – 220/66 kV Substation
- G Fault to MEN from 11 kV Overhead line
- H Fault to MEN from 11 kV Buried Cable
- I Historic Substation Protection Practices (pre 1989)
- J References
NEUTRAL EARTHING RESISTORS/REACTORS (NER) GUIDE 180121: This guide sets out recommended planning, design, and installation practices which should be followed when it is desired to install neutral earthing resistors/reactors (NER’s) 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 focused on the use of NER’s 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 NER’s for any purpose.
A comprehensive coverage is given, not only for the use of NER’s 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 NER’s 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.
NOISE GUIDE 180121: 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.
POWER COORDINATION HAZARD ASSESSMENT GUIDE: GUIDE FOR ASSESSMENT OF RISK OF EPR AND INDUCED VOLTAGE HAZARD TO TELECOMMUNICATION NETWORKS – DRAFT 2023 (NEVER PUBLISHED)
Abstract
This guide provides criteria for assessing hazard voltage-time duration values on telecommunication networks, for both EPR and induced voltages, and provides guidelines for assessing the need for mitigation. The guide discusses:
- Legislative Requirements
- Means of Compliance:
- Compliance Approach as Currently Deemed Acceptable
- Compliance Approach Based on ITU-T Recommendation
- Consideration of Voltage-Time Values Exceeding ITU-T Targets
- Experience with High-Value Low-Risk EPR Situations
- Determination of Prospective EPR & Induced Voltages
- Risk Assessment Process
- Example Risk Analysis for Power HV Network Fault on Concrete Pole near Telecommunication Equipment
- Derivation of ITU-T Recommendation K53 Limits
This guide has never been formally published. However it has been retained because it contains useful discussion on New Zealand and European Power Coordination EPR and induced voltage limits, and associated international standards.
POWER COORDINATION OVERVIEW GUIDE: GUIDE FOR EVALUATING AND ADDRESSING ADVERSE INTERACTIONS BETWEEN POWER AND TELECOMMUNICATIONS SYSTEMS (V2.0 MAY 2022)
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:
- Assumed minimum insulation levels of different Chorus telecommunications network cable types.
- 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 Telecom 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.
SINGLE WIRE EARTH RETURN (SWER) HIGH VOLTAGE POWER LINES APPLICATION GUIDE: Guide for the control of interference to telecommunication circuits (1999)
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 CONTINUOUSLY carry 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.