Puhoi Area Vector Network Reliability October 2014 - Puhoi NZ

Vector Network Reliability
Puhoi Area
                             October 2014

Background

   The Puhoi region is supplied by two HV
    feeders; the Waiwera feeder which
    originates from Orewa (brown) and the
    Satelite which comes from Warkworth
    (red).

   Each feeder exceeds 100km in length and
    is predominantly overhead.

   Both feeders are classified as rural, in total
    they supply 2,021 connections.

Puhoi Village

    The two feeders meet at the Puhoi Village, the
     Southern end is supplied by the Satellite feeder
     and the Northern end receives power from
     Waiwera.

    There is an 'open point' between the feeders, this
     can be closed to allow power to be back-fed when
     required.

    Each side experiences different outages.

Service Levels

                    The level of service we are able to provide
                     depends on where you live.

                    Urban homes have fewer faults on average
                     and are shorter in duration than rural
                     feeders

                    This is due to the length and exposure of
                     rural overhead lines and a number of
                     factors that are largely outside our control
                     such as:
                     • Severe weather conditions
                     • Bird strikes
                     • Car vs pole accidents
                     • Vegetation

Unplanned Outage Causes

   Note: 38% of faults on the Northern end and 57% of faults on the Southern end occurred during
   storm periods.

Unplanned Outage Durations

Distribution of Outages - Count

   This plot shows the distribution and count of
    fault outages over the last two years.

   Puhoi is near the end of both feeders so
    unfortunately experiences relatively poor
    reliability.

   Outage counts over the last 12 months have
    been high, largely due to the four major
    storms earlier this year;
    •   14-17 March
    •   17-20 April
    •   10-16 June
    •   8-12 July

Distribution of Outages - Duration

   This plot shows the cumulate duration of all
    fault outages over the last two years. Values
    are in hours.

Preventative Maintenance
   Vector has a comprehensive preventive maintenance
    program with standards regarding;
    •   Inspection Tasks.
    •   Test Activities.
    •   Maintenance Servicing.
    •   Condemned Pole Assessment.

   Feeder maintenance and replacement tasks are driven
    by asset condition and risk.
    •   There have been 6 HV outages caused by conductor failure on the
        spur line to Wenderholm Regional Park from 2011 to 2014. We have
        recently completed a conductor replacement exercise removing the
        problematic 16mm Cu conductor.
    •   In addition, Wenderholm is locked after-hours with no vehicle
        access to patrol/repair the line. Over the coming months we plan to
        install additional DDOs (fuses) before the line enters the park,
        splitting the protection on this spur line and improving restoration
        times.

   New inspection technologies are constantly being
    assessed. New-generation ultrasonic pole surveys were
    introduced in 2013.

Tree Trimming
            At least 1/3 (& up to 3/4) of all faults* are vegetation-related.
            Vector has a Regulatory obligation to maintain safety clearance distances around electricity lines.
              Tree owners have regulatory obligations to trim their trees in accordance with these safety clearances
            As part of our historical tree inspection cycle, Vector last undertook network inspections, issued CTNs
              and then trimming in:
             •    38SATE: 2006/2011/underway
             •    26WAIW: 2009/2013/underway
            Our 2014 feeder tree survey’s identified two sets of works:
             •    Trees currently breaching Regulatory clearance distances from electricity lines
                   −   Tree owners (private or Council) will be issued with regulatory Cut Trim Notices to restore clearances (at their
                       cost)
                            38SATE: Private: 24 sites = 145 trees          & Council: 7 sites = 63 trees
                            26WAIW: Private 17 sites = 159 trees           & Council: 5 sites = 15 trees
                   −   Where these are ‘first cuts’ Vector will be undertake the works for the tree owner (at our cost)
                            38SATE: 14 sites
                            26WAIW: 6 sites

             •    Trees that pose a risk to the network (outside of regulatory safety clearance distances)
                   −   Identified trees that have a high-risk of causing a fault due to: flying debris/broken branches, tree fall hazard
                   −   We will be liaising with each private tree owner to agree trimming or removal requirements, and Vector will
                       contribute to the cost depending on what is agreed.
                            38SATE: Private: 5 sites = 67 trees
                            26WAIW: Private: 25 sites = 155 trees

            Tree owners will start receiving letters soon, and we request they contact the Treescape liaison person detailed on the
             letter to work through the detail of the tree trimming works required.

        * 33% of faults were verified as vegetation issues. In addition 40% of faults were ‘transient’ - a high proportion of them will be vegetation related.

Protection Scheme Review

   Protection systems do not prevent feeder
    faults, but do minimise their impact.

   Both feeders supplying Puhoi have
    sophisticated, multi-tiered systems
    including automated devices and numerous
    HV switches and fuses.

   The feeders are being reviewed to further
    refine the system and leverage
    technological developments.

   Additional fuses, sectionalising fuses and
    isolation points will be installed at optimal
    locations.

Electrical Safety
General
   Report any hazards to 0508 VECTOR (0508 832 867).
   Broken lines - Treat all power lines as live at all times and keep everyone well clear
    of the area.
   Arcing/sparking Equipment – Keep clear, report immediately.
   Car vs Pole - If lines are down stay in the car until help arrives. If forced to
    evacuate, jump clear. Do not to touch the vehicle and the ground at the same time.

Working Safely
   Minimum safe work distances;
    •   >4m from OH lines
    •   >5m from a pole when digging
    A close approach consent is required to work closer.
   High Loads - You must apply for a high load permit if you plan to move any tall
    structure such as a house or a boat.
   If you are unsure about anything before you start any work near our networks call
    0508 VECTOR (0508 832 867) or visit www.vector.co.nz and download ‘A guide for
    working safely’.

Questions?