Implementing Predictive Distribution Maintenance Using a Universal Controller Francisc Zavoda, Réjean Lemire, Chad Abbey Electrical Equipment Research Institute of Hydro-Quebec Varennes, Québec, Canada
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[email protected], Abstract—Traditionally, on-line condition monitoring, a subset of condition based maintenance (CBM) or just in time (JIT) maintenance, was applied only to transmission substation equipment. Recently, the evolution of technologies such as: sensors, intelligent electronic devices (IED) and wireless communication, has created the possibility for implementing predictive maintenance in distribution as well. Standardization of different major distribution equipment (MDE) controllers is the first step in leveraging their potential implying interoperability, interchangeability, development and implementation of smart distribution applications (SDA) including predictive maintenance. This paper describes the advantages of a standardized universal controller, based on a modular concept, on distribution maintenance, namely on implementing the more efficient and less costly JIT maintenance.
Load switches,
Capacitor banks.
Index Terms-- Smart Grid; Smart Distribution Applications; Just in Time Maintenance; sensor; standardization; plug and play, interoperability, interchangeability. Figure 1.
I.
Major distribution equipment and their controllers
INTRODUCTION
One of the main characteristic of the Smart Grid is an increased acquisition, from the grid itself, of data whose accuracy and reliability strongly depend on sensors and intelligent electronic devices connected to the grid [1], [2]. These data became more and more important, being used by Smart Distribution Applications (SDA). Some of them such as: Volt & VAR Control, Volt & VAR Optimisation, Fault Location have already been implemented by leading utilities and some others namely: Feeder Reconfiguration, Integrated Power Quality Monitoring will be in the near future. New investments in data acquisition equipment are heavily impacted by budget constraints, so leveraging part of the existing equipment is a valuable approach. In distribution, the leverage process targets mainly the controllers of major distribution equipments. These intelligent electronic devices are capable of measuring and monitoring voltage, current and related parameters. There are four different types of MDE (see Figure 1):
Reclosers,
Voltage regulators,
On-line condition monitoring, a subset of condition based maintenance or just in time maintenance, has typically only been applied to transmission substation equipments, due to the high cost of the transducers and IED involved. Maintenance of distribution equipments has been limited to reactive and preventive activities. Recently, budget reductions in distribution maintenance pushed utilities to find new approaches for MDE maintenance. It is hoped that recent evolution of technologies such as: sensors, IED and wireless communications, will facilitate implementation of predictive maintenance in distribution as well. One of the SDA, which is closely evaluated and has good chances of being implemented in the near future, is predictive maintenance of MDEs. This SDA is based on embedded sensors connected to the MDE’s controller, which communicate remotely with the maintenance service center. This paper discusses the potential impact of a new concept of feeder level universal controller/IED on MDE’s maintenance. This universal IED has modular structure and
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Reconfiguration, real-time integrated PQ Monitoring, JIT Maintenance), which will be developed in the near future.
should be compatible with each type of MDE. II.
MDE CONTROLLER
A. Classic Controller The role of classic controllers (see Figure 2) was to control and command the major distribution equipment, which was operating as standalone, or to allow technicians to perform manually and locally grid operations.
There are a number of hardware components that combine to provide the functionality of the controller. The required hardware includes: 1) Housing rack: Each electronic card would be mounted on nineteen inch standard rack mount system or a 9.5 inch standard half rack used by leading manufacturers. All interface connectors should be embedded in the rack eliminating the need for manual wiring connection. This approach should facilitate the modular design of the controller and its plug and play functionality. 2) User Interface: The touch screen electronic tablet, which replaces the classic “Front Panel”, is used to:
Figure 2.
Example of cabinets
Each MDE includes a medium voltage device (MVD) and its controller, which comes in a large variety of sizes and types of metal enclosures. The controller is located in a pole-mounted cabinet or is integrated in the body of MVD (see Figure 3). In the pole-mounted configuration, the cabinet contains also ancillary parts, including the battery for the backup power supply.
Configure locally the controller,
Operate the MDE and obtain information regarding its settings, status and health.
Figure 4.
Example of touch screen electronic tablet
This handheld device (see Figure 4) interfacing with the controller through a wireless communication channel compatible with either type of controller, pole-mounted or integrated into the body of the medium voltage equipment, will reduce problems associated with security and tampering. a) Figure 3.
b)
Controller mounting options: a) pole mounted cabinet; b) integrated into the body of MVD
At this time, among controllers, there is a very low degree of interoperability and none are interchangeable. B. Universal controller To improve reliability, efficiency, security and reduce the maintenance time and maintenance cost in distribution, a new concept of controller was proposed in [4], [5]. The new controller would be modular and standardized in terms of its hardware and software and what functionalities it can offer. It will also offer better cyber security [6]. In this way, it could be automatically configured to the distribution equipment to which it is physically connected, recloser, voltage regulator, load switch or capacitor bank, but also—through the telecommunication network and enterprise service bus—to the SDA (Volt & VAR Control (VVC), Fault Location, FLISR, etc.) to which it is associated. Some manufacturers have been already moving in this direction, offering possibilities for standardization. An important characteristic of a modular controller is the ability to do maintenance and hardware and software version upgrades, with minimum investment and maximum hardware reuse. It should also enable real-time information for grid operation and maintenance, and provide historic data for analysis and planning. Its open platform concept increases the ability to integrate new smart distribution applications (Feeder
3) Main board (including CPU + FPGA): This card is the main circuit board, which processes measured data in real time and executes the firmware, which realizes the main function (protection, voltage regulation, feeder reconfiguration, VAR management). Flexible and reconfigurable architecture, the card provides deterministic applications and synchronization. 4) Communication interface: The communication card through wired and wireless technologies allows to exchange operational and maintenance data between the main board and the distribution control center (DCC) or maintenance service center (MSC), using different standard protocols [7], [8], [9]. 5) Power supply: The high performing power supply card controls and manages the power needs of controller and in certain cases of equipment itself. The intelligent system acts also as a universal battery charger-analyzer and the results of its periodic diagnostic test on battery status are sent to MSC. 6) Voltage and current inputs: This card performs the analog to digital conversion of signals coming from voltage and current instrument transformers and send them to the main board for processing. 7) Sensor electronic interface: This card interfaces different analog and digital sensors such as: temperature, speed, displacement, proximity, etc. and sends the digital data to the main board for processing. 8) Input/Output contact blocs: This card offer isolated digital input channels as well as isolated digital output
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channels with isolation protection controlled by the controller firmware, which are used to integrate the MVD status or other verifications. III.
UNIVERSAL CONTROLLER STANDARDIZATION
The implementation of this concept depends significantly on the success of an international standardization process, which would help reach a consensus among utilities and controller manufacturers. A generic specification for the universal modular controller was written [5] in order to facilitate eventually the development of an international standard. The process will involve working groups (WG) under the umbrella of recognized international organizations such as IEEE and IEC. The specification consists of:
Controller hardware including the rack, electronic cards and accessories,
Software (firmware, interface applications),
Extended battery lifetime (10 year) for back-up power supply.
It outlines a modular hardware and software design, based on a standard rack, which accepts standard electronic cards and provides plug and play, interoperability and interchangeability characteristics. The degree of the standardization process, with respect to the modular design of the universal controller, will be a matter that concerns experts from utilities and manufacturers, who will be working together, as members of above mentioned WG, to deliver the standard. IV.
MDE MAINTENANCE The MDE maintenance includes:
Hardware maintenance (MVD + controller),
Software maintenance (controller firmware, interface applications).
The universal controller will monitor the network and the MDE and will record different parameters useful for smart distribution applications including the predictive maintenance of the MDE. A. MVD maintenance Presently, some MDE are offered with embedded current, voltage and other types of transducers. Practically, these sensors allow basic functionalities in controllers, supporting predictive maintenance such as:
Maintenance algorithm: Used to check the LTC taps based on a defined algorithm.
For example, the contact wear monitor function is based on the capability of some controllers of storing and updating information related to the number of trip operations of the recloser. This type of controller accumulates the number of trips and integrates the number of close-open operations and the per-phase current during each opening operation. Afterwards, it compares the integrated close-open information to a predefined breaker or recloser maintenance curve to calculate the percent contact wear on a per-phase basis [10]. The universal controller will allow MDE manufacturers to integrated new low cost sensors such as: temperature, speed, displacement, proximity, etc. into the major distribution equipment. These signals will be collected and analyzed by the controller and used to improve the MDE maintenance in general. This will facilitate implementation of just in time maintenance, among other SDAs. B. Controller maintenance At regularly scheduled intervals or when there is an indication of a problem with the controller, maintenance tests are performed to ensure that the IED is measuring accurately a.c. quantities, and scheme logic, protection elements and auxiliary equipment are functioning correctly. However, the controller is equipped with reliable self-testing capabilities and detailed metering and event reporting functions reducing the dependence on routine maintenance testing. Any failure is recorded in a table event log and a warning or an alarm message is sent to the DCC or the MSC. If the failure does not compromise the protection, the controller notifies the DCC or the MSC but continues to operate. Otherwise, if the protection is compromised the equipment is taken out of service and an alarm is sent to the DCC or the MSC. 1) Hardware maintenance In case of a faulty controller, existing maintenance practices include the replacement either of pole-mounted cabinet or of the controller itself. Due to modular structure of universal controller, future practices might also include the replacement of any electronic card from the controller rack. a) Replacing the cabinet This type of maintenance consists in replacing the entire cabinet (see Figure 5) containing controller, protections, battery, heating system, etc. It is the existing practice most common among utilities.
For circuit breaker/recloser:
Operation counter: Total operations for the three phases and ground, Contact wear monitor: Stores the number of recloser contact opening and closing operations and fault currents.
For voltage regulator:
Tap position: Time (%) spent by tap changer on each tap,
Figure 5.
Example of functional cabinet
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After turning off the power line, control and power cables connected to the cabinet are disconnected and the existing pole-mounted cabinet is removed. A new preconfigured package identically to the original is reinstalled.
near future. All cards are easy removable without tools. These cards are plug-and-play, allowing the technician to perform the replacement by connecting a new card without prior configuration.
The following table lists the advantages and disadvantages of replacing the cabinet. TABLE I
PROS AND CONS OF REPLACING THE CABINET
Advantages
Disadvantages
Replacement cabinet is tested in the maintenance shop by a qualified technician or electrician in a friendly environment prior to installation.
The most expensive maintenance practice requiring more maintenance personnel (linemen, electrician or technician). Requires disconnection, reconnection, and handling of the cabinet. Mechanical shocks and vibrations during transportation and installation can damage the cabinet or parts of it. The most onerous in terms of hardware costs, inventory requirements and storage space.
b) Replacing the controller This type of maintenance, replacing the faulty controller including all electronics cards on the spot by turning the equipment off (see Figure 6), is an existing practice less used by utilities.
Figure 7.
Example of rack containing some electronics cards
The replacement of faulty cards can be done using either new cards from the same manufacturer or replacement by new cards from a different manufacturer. The latter is true in an ideal situation when there is interoperability between the cards from different manufacturers. The advantages and disadvantages of replacing electronic cards are illustrated in Table III. TABLE III
PROS AND CONS OF REPLACING CARDS
Advantages Job requiring less personnel (only done by a maintenance technician), reduction of handling costs.
Disadvantages Installation is dependant on weather conditions.
The cabinet is not disconnected from the MVD avoiding the possibility of further damages. The least time to repair (swap the faulty card by a new card and no wiring connections required). The easiest to manipulate and to protect against damage.
Figure 6.
Examples of controllers
Table II presents the advantages and disadvantages of replacing the controller. TABLE II
PROS AND CONS OF REPLACING THE CONTROLLER
Advantages Job requiring less personnel (only done by a maintenance technician), reduction of handling costs, easier to handle and to protect against. The cabinet is not disconnected from the MVD avoiding the possibility of further damages.
Disadvantages Installation is dependant on weather conditions. Longer installation time. Controller is moderately difficult to handle.
Controller is more easy to handle than the cabinet. Less onerous in terms of hardware costs, inventory requirements and storage space.
c)
Replacing electronic cards
This type of maintenance is to replace the defective cards in the universal controller (see Figure 7). This philosophy has yet to be implemented by utilities but might be considered in the
Least onerous in terms of hardware costs, inventory requirements and storage space. Easy to upgrade hardware.
In all three maintenance practices discussed, before connecting the controller to the MDV, its functionality should be validated. This is typically done in the field using some sort of intelligent testing device. Upon validation, the controller can then put back in service. 2) Software maintenance The software maintenance covers both the firmware and the interface applications. The firmware is loaded into the controller. The interface applications are loaded into the tablet or into the distribution management system (DMS) at the grid control center. In case there is no DMS, it can be loaded into the maintenance system used at the maintenance control center. The controller firmware can be updated locally, via the tablet or remotely via a wired or wireless network by an authorized user. As the material is flexible and reconfigurable, it is easy to add extra new functions on the controller and the tablet. The tablet’s interface applications will be able to show a simple graphical user interface adapted to the function of the
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IED: plug and interchangeability.
user (operator, maintenance technician, etc.) and the type of MDE (recloser, voltage regulator, load switch, capacitor bank). With multiple access authorizations based on the user levels, the security is improved. As there is no possibility to control the device from the front panel located in the cabinet, the risk of intrusion by an unauthorized person is reduced The possibility of standardizing user interfaces of different manufacturers can minimize the MDE operation and configuration errors. The touch screen tablet facilitates customization and update of the GUI because it is much easier to change the programming code to display a new user interface than to change the physical hardware, namely the front panel of the controller. The controller maintenance software runs in background and must be able to detect a faulty card and to send a report to the DCC and to the MSC. V.
UNIVERSAL CONTROLLER IMPLEMENTATION
As the new universal controller is modular, it is easy to upgrade hardware at a minimum cost. Investing in software updates to add new features is preferable to physical upgrades of the distribution network. The universal controller will provide many benefits, but its implementation hinges on the successful collaboration of industry. Table IV summarizes these considerations. TABLE IV
BENEFITS AND CHALLENGES OF THE UNIVERSAL CONTROLLER Benefits
Challenges
More efficient personel training and operation and maintenance Improved cybersecurity (hardware and software) Ability to scale hardware and software features to improve the continuity index of the network Ease of use
Reaching a consensus between manufacturers and utilities through international working groups Standardization of the universal controller concept Implementation in smart grid applications
Low cost upgrades Spare parts available at low cost Low inventory requirements at the electric company Facilitate deployment of smart distribution applications
CONCLUSIONS Implementing this IED will significantly facilitate the implementation of JIT maintenance in power distribution and lead to following benefits:
Optimizing assets and workforce management by time and cost reductions on equipment, maintenance personnel training and procurement,
Hardware and software complying with international standards,
Improving system security, reliability and risk management,
Flexible integration of IEDs in smart grid applications due to the three crucial characteristics of the universal
play,
interoperability,
It is important that an international working group takes care of specifying the universal controller, which requires coordinated effort in that direction by utilities and manufacturers alike. REFERENCES [1]
F. Zavoda and G. Simard, “Performance of Today's Intelligent Controllers and Meters, Elements of an Integrated Monitoring System for ADA”, IEEE PES GM, Pittsburg, USA, July 2008. [2] F. Zavoda, “Using Major Distribution Equipment Controls for PQ Monitoring (MV) at Feeder Level”, presented at Conf. DISTRIBUTECH – Empowering the future, San Diego, USA, February 2011. [3] F. Zavoda, “Sensors and IEDs required by smart distribution applications”, The First International Conference on Smart Grids, Green Communications and IT Energy-aware Technologies (ENERGY 2011), Venice/Mestre, Italy, May 22-27, 2011. [4] F. Zavoda, C. Abbey, Y. Brissette, R. Lemire, “Universal IED for Distribution Smart Grids”, CIRED, Stockholm, Sweden, June 2013. [5] F. Zavoda, C. Abbey, Y. Brissette, R. Lemire, “Universal cotroller for Smart Grid”, IEEE PES GM, Vancouver, Canada, July 2013. [6] Draft Standard for Intelligent Electronic Devices (IEDs) Cyber Security Capabilities, IEEE Draft Standard P1686™/D, 2013. [7] Communication networks and systems for power utility automation – Part 6: Configuration description language for communication in electrical substations related to IEDs, IEC International Standard 61850-6, Ed. 2.0, Dec. 2009. [8] IEEE Standard for Electric Power Systems Communications -Distributed Network Protocol (DNP3), IEEE Standard 1815-2010, July 1, 2010. [9] Application integration at electric utilities – System interfaces for distribution management – Part 13: CIM RDF Model exchange format for distribution, IEC Standard 61968-13, 2008. [10] SEL-651R Recloser Control Instruction Manual *PM651R-01 Schweitzer Engineering Laboratories, August 2006
BIOGRAPHIES Francisc Zavoda (M’09) graduated from Bucharest Polytechnic Institute in 1979 and got his MASc degree in Electrical Engineering in 1995 from École Polytechnique de Montréal. He is a senior research engineer at HydroQuébec’s Research Institute. After graduating, he worked for ISPE Bucharest, a consulting company for Romanian Power Department. In 1990, he joined Siemens Canada Power Department. He’s with Hydro-Quebec`s Research Institute since 1995. In the PQ field, he participated in the development of the PQ Measurement Protocol and a power quality analyzer. He was responsible for a susceptibility survey project, a harmonic contribution discrimination project, a DA data acquisition project and participated to a Fault Location and VVC project. He is presently in charge of projects related to PQ, Smart Grid and Advanced Distribution Automation (ADA) programs. He is a member of several CIGRE/CIRED and IEEE WG. Réjean Lemire received the B. Sc. degree in electrical engineering from Université de Sherbrooke, Sherbrooke, QC, Canada, in 1987. Currently, he is an Engineer at the Institut de recherche d’Hydro-Québec (IREQ), Varennes, QC, Canada. He works mainly on systems design. He also worked on developing sensor and measurement system of high voltage and high current. Mr. Lemire is a member of the Ordre des Ingénieurs du Québec. Chad Abbey (M'01) received his M. Eng degree from McGill University, Montréal in 2004, and in 2009 he completed his Ph. D. at the same institution. He works at the Hydro-Quebec Research Institute as a research engineer in the areas of advanced distribution systems and smart grids. His current research interests include advanced distribution systems, distributed generation, and energy storage. He is an active member of CIGRE and the IEEE.
