It is proven that the more time and effort spent planning and preparing for shutdown the better the outcomes. Here is our simple guide to taking the guesswork out of mine shutdown management by looking at some of the common electrical issues faced along with some helpful tips to ensure you get back up and operational, on time and on schedule.
AS/NZS2081 and AS/NZS4871 present competing requirements for the application of earth continuity protection in earth fault limited mining systems. AS/NZS2081 requires that earth continuity protection be capable of operating within 100ms to quickly protect an outlet in case of live uncoupling. Meanwhile, both AS/NZS2081 and AS/NZS4871 require that the earth continuity protection should also be capable of monitoring incremental changes in the resistance of the earth return path to ensure that leakage currents do not result in dangerous touch potentials. It is sometimes not possible to achieve a practical earth continuity protection system that satisfies both of these requirements, if static time and trip settings are used.
We’ve developed a new method of earth continuity protection that utilises a ‘trip curve’ to discriminate between earth disconnection faults and incremental increases in the earth return impedance that occurs due to equipment degradation. Using this method it is possible to provide an “instantaneous” trip for energised uncoupling of cables that significantly reduces the chance of an arcing fault or exposure to live terminals. For gradual increases in the impedance of the earth return path, a time delay is introduced to allow discrimination between noise induced onto the cable’s pilot-earth loop, and an actual increase in loop impedance.
Take a fresh at earth continuity, safety and AS/NZS2081 in this downloadable PDF or watch the below presentation.
Following the short circuit failure of one of their two specialist furnace transformers, Moly-Cop urgently required the installation of a replacement. It was decided that an existing spare transformer that had been in storage for 15 years could be modified to suit the special requirements of the furnace.
- Reworking the external bus bar arrangement and fitting a new off circuit tap changer and HV cable box
- Transformer overhaul, including installation and commissioning of the transformer in a very short timeframe, reducing disruption to site production
- Engagement with site personnel to coordinate the multi-discipline site installation requirements
After initial inspection a detailed work schedule and execution plan was established and agreed with onsite personnel to match the site specific production initiatives.
Given the age of the transformer and the time it had been in storage it was in need of major repair and upgrading to meet the demands of the critical role it has in production.
Modifications and upgrades included the following:
- Replacement of compound cable box with new plug in type to suit site cabling
- Modification of the transformer design to suit an off circuit tap switch including removing the existing on load tap changer which was not fit for service repair.
- Redesign and accommodation of a pumped water cooler sourced from a separate on-site transformer.
- Design and manufacture of external busbar system to configure the correct vector connection and couple it to existing site bus-work
- Inspection and processing of the core and coils together with the supply of new transformer oil
- Refurbishment of the existing conservator and pipework
- Reconfiguration of a new control box, wiring and auxiliary protection devices.
The busbar design required significant engineering to ensure the weight of the busbar was supported and to minimise stress on the transformer bushings. Flexible connections were manufactured from copper sheet punched and formed to individually align with the multiple bushings of the transformer. This high current externally connected structure required support both at the top and bottom with the bottom supports designed to accommodate for uneven floor and alignment to the existing busbar.
Close coordination with the site personnel was required to ensure delivery of the project within the agreed schedule as well as to coordinate both transformer specific design changes and modifications to accommodate the new larger footprint of the transformer
Through close participation with the site personnel and coordination by the project team this turnkey, labour intensive, multi-discipline project was successfully delivered in a short timeframe.
Find out more about Ampcontrol’s transformer engineering and manufacturing capabilities
The ECM2 Earth Continuity Relay has been discontinued and is no longer available, it has been replaced by the ECM3.
The ECM3 relay is a direct drop-in replacement for the existing ECM2 relay, no additional wiring necessary.
The ECM3 relay will operate with either an existing ECM2 remote termination unit or the new ECM3 termination unit, with identical characteristics. This means termination unit upgrade will not be necessary.
Find out more about ECM2 obsolescence and support.
About the ECM3
The ECM3 is an earth continuity protection relay designed with AS/NZS 2081 (2011) and AS/NZS 4871.1 (2012) in mind. It has superior touch potential monitoring and noise immunity and overcomes the performance degradation experienced by the EMC2 when exposed to significant pilot noise – Find out more about the ECM3.
The ECM3 implements earth continuity protection using a unique Earth Continuity Trip Curve, whereby the magnitude of the fault is related to the speed of trip actuation – Find out more about this innovative approach