Static Var Compensators for Mining Enhancing Your Process Economy Feeding Safe and Reliable Power to a Mine Is a Challenging Task

ABB FACTS – Flexible AC Transmission Systems Static Var Compensators for Mining Enhancing your process economy Feeding safe and reliable power to a mine is a challenging task. Mines are often remotely located and fed by weak networks. This in combination with heavy and complex mining loads creates problems with both reliability and power quality. An SVC (Static Var Compensator) can increase the overall stability of the system, improve the power quality and also enhance your efficiency and productivity.

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2 Static Var Compensators for Mining | ABB FACTS Enhance your process economy with SVC

Mining loads and the electrical grid The Static Var Compensator Operating a mine is a complex task which requires careful The ABB Static Var Compensator( SVC) provides dynamic planning in order to secure a high availability of the equipment voltage support and makes mining possible even in remote and a stable production rate without costly production locations with weak grids. The SVC mitigates system outages. A difficult part is the mine’s electrical network. disturbances and enables an increased productivity by The network needs to support various loads with different stabilizing the system voltage. requirements on power quality. As mines get larger and more remote, the need of voltage support becomes critical. The In short, the SVC is a device which can dynamically control SVC will improve network stability and reliability resulting in a the reactive power flow and voltage in an electrical network. more efficient mine process. It is based on advanced semiconductor technologies in combination with harmonic filters. The heart of the SVC is You will experience benefits in terms of: the thyristor valve and the control system which are used to −− Increased utilization of the equipment dynamically control the voltage. The control system constantly −− Power factor correction monitors the system and makes sure that just the right −− Mitigation of harmonics, unbalance and voltage variations amount of reactive power exists in the network and that the −− Reduced risks of unnecessary tripping voltage is kept at a constant level. −− Grid code compliance −− Reduced transients at startup of heavy equipment −− Better voltage stability −− Increased transfer capacity

Close up view of SVC system 6

5 The SVC solves power quality problems for each application.

11. Mine hoists 44. Motor heavy load - Fluctuating load - Poor power factor - Huge reactive power consumption at (~0.75 p.u.) start up (DC-drive) - Large inrush current - Harmonics - Over-voltages at load rejection

22. Grinding machines 55. Smelters - Fluctuating reactive power demand - Flicker - Dynamic harmonic spectrum - Unbalance (cycloconverter driven) - Harmonics - Very large dominating load (20–30 MW) - Reactive power demand

33. DC/AC Drives 66. Incoming transmission line - Harmonics - Weak feeding network - Notching - Voltage dips - Reactive power demand (DC) - Voltage peaks - Voltage fluctuations (DC) - Voltage fluctuations

ABB FACTS | Static Var Compensators for Mining 3 Optimizing your mine’s electrical network Increasing both reliability and efficiency

Better voltage stability Lower losses An SVC reacts to external disturbances within milliseconds By installing an SVC, no reactive power is drawn from the and will support the system during grid faults or in cases of transmission system resulting in lower losses in the system load rejections in the mine. This provides a better voltage and the transformers. Through a higher bus voltage, the stability and the mine will be less prone to unnecessary motor losses will also be reduced. tripping of equipment. Increased transfer capability Higher efficiency and unity Power Factor When no reactive power is taken from the grid, more active The SVC will stabilize the medium voltage bus of the mine power can be transferred over long distances to the mine. and increase the power factor to unity. This will increase This makes mining expansion possible, also in remote areas, the efficiency of the equipment since this should always be without the need of new transmission lines. operated at rated voltage.

SVC features Your bene ts

A mine more immune to grid faults. Thus, less 1 Increased the stability margin trips of equipment!

2 Higher voltage at the point of operation More power available for the mining equipment!

Increased maximum active power that can be 3 More power available for the mining equipment! consumed by the mine

Bus voltage with SVC Operating point U Bus voltage without SVC

P-MAX 2 1 Stability margin 3 Critical Voltage

The plot above illustrates the main bus voltage(U) as a function of the mine’s actual power consumption(P) at a given time. Without an SVC the bus voltage starts to decrease as soon as the loads start to consume power. With an SVC this voltage drop is reduced contributing to numerous advantages.

SVC versus Fixed filter banks Advantages of the SVC compared to fixed compensation Traditionally, harmonic filter banks have been used to −− Increased stability margin compensate for the inductive loads of the mine site. −− Increased active power transmission However, there are several limiting factors restraining −− Phase-wise compensation and unbalance control the performance of such installations. The lack of −− No penalties from utility for poor power factor dynamic response of the filter banks cannot counteract −− Higher utilization rate the fast variations in reactive power and the risk of −− Mitigation effects of faults/disturbances over-voltages are restricting the size of the filters, −− Stable feeding voltage leading to a low power factor and low utilization rate of −− Reduced transformer size the mining equipment. −− Less winding heating in motors

4 Static Var Compensators for Mining | ABB FACTS Power quality

A weak grid in combination with heavy With an SVC you can: loads, harmonic emissions and a −− Keep a constant power factor and voltage complex cable network cause problems −− Reduce harmonics in the system with power quality. By stabilizing the −− Mitigate transients such as inrush currents and voltage and at the same time making voltage dips/peaks −− Balance an unbalanced system (Negative phase sequence use of harmonic filtering capabilities of control) the SVC, many of these problems can −− Damp flicker be solved. The SVC will enhance and −− Improve power tariffs safeguard the production capability. −− Comply with grid codes

Example of Voltage improvement at a large Iron ore mine in Sweden after installing an SVC:

Without SVC With SVC

U [V ] U [V ] 4000 4000

3800 3800

±2% 3600 ±10% 3600

3400 3400

U1 Min U1 Min U1 Max U1 Max 3200 Time 3200 Time 08:20:00 08:25:00 08:30:00 08:35:00 08:40:00 09:35:00 09:40:00 09:45:00 09:50:00 09:55:00 10:00:00 10:05:00 10:10:00

The dynamic behavior of the loads causes severe voltage fluctuations An SVC mirrors the behavior of the loads, reducing the voltage fluctua- without any dynamic support. tions from ten to two percent.

ABB FACTS | Static Var Compensators for Mining 5 SVC Components

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Thyristor valve Control & protection system The semiconductors are controlled on a millisecond basis in order to optimize The control system is the brain of the SVC, constantly monitoring the system to the voltage profile on the bus and control the reactive power flow. The same make sure it is operated under optimal conditions. ABB uses the same control technology is used for HVDC applications involving very high currents, ultra-high system as in demanding HVDC applications. The control system has built-in voltages and having the highest demands for reliability. redundancy to ensure highest availability.

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Cooling system TCR (Thyristor Controlled Reactor) The cooling system is needed to cool the semiconductors. It can either use a This reactor is in series with the semiconductor valve. It is by controlling the cooling tower or, where available, industrial process water. current through the TCR that the reactive power is controlled.

6 Static Var Compensators for Mining | ABB FACTS 4 5

7 1 3 2

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Harmonic filters SVC building The harmonic filters have two objectives. Firstly, to supply capacitive reactive The SVC building can be prefabricated in order to save time and cost during power to the network. Secondly, to filter unwanted harmonics. both civil works and installation.

Connection of the SVC An SVC can be connected to the medium voltage bus by either cables or busbar. If there is limited space in the substation, the SVC yard can be placed up to 1 km away and be connected by cable. Alternatively, the SVC can be connected on the high voltage system through a transformer.

ABB FACTS | Static Var Compensators for Mining 7 Application example: Mine hoists SVC enabling a 25–30 % increase of hoisting capacity.

kV The LKAB mine in Kiruna, Sweden, is one of the largest kV 3.9 3.8 underground iron ore mines in Europe with an annual 3.7 kV 3.63.9 production of 25 million tons. Due to a weak network and 3.53.8 kV 3.43.93.7 strict power quality requirements, the full hoisting capacity 3.33.83.6 could not be used. In order to limit the voltage variations and 3.23.73.5 3.13.63.4 assure safe operating conditions only one of the seven mine 3.03.53.3 MW 3.43.22.4 hoists could be accelerated at a time. 3.33.12.2 3.23.02.0 MW 2.4 3.1MW1.8 3.01.62.2 In order to increase the hoisting capacity, LKAB installed MW 2.41.42.0 1.8 an SVC to provide the reactive power needed to accelerate 2.21.2 2.01.01.6 the mine hoists. The SVC stabilizes the 6.3 kV bus voltage 1.80.81.4 1.60.61.2 reducing the voltage variations from about ten percent to 1.40.41.0 1.20.20.8 less than two percent. The installation made it possible to 1.00.60 MVAR 0.82.40.4 accelerate three hoists simultaneously, enabling a production 0.62.20.2 0.42.00 capacity improvement of 25 – 30 percent. MVAR 0.21.82.4 1.62.20 MVAR MVAR2.41.42.0 The SVC was designed for the mining environment and winter 2.21.21.8 2.01.01.6 conditions in the north of Sweden with extreme temperatures 1.80.81.4 1.60.61.2 (- 40 C) and dust. To facilitate a quick installation and minimize 1.40.41.0 1.20.20.8 the civil work, the building was delivered as a prefabricated 1.00.60 0.4 container. After the first successful installation, ABB has now 0.8 0.60.2 equally successfully delivered and commissioned a second 0.40 0.2 SVC for LKAB. 0

Illustration of a mine hoist load cycle. The sharp peak in reactive power during start-up of heavy equipment can lead to under-voltages and tripping of protections as well as system insta- bility. The SVC rapidly responds to the peaks and counteracts the effect on the power system.

The SVC installed at LKAB in Kiruna, Sweden, improves power quality and enables a production increase.

8 Static Var Compensators for Mining | ABB FACTS Application example: General voltage stability SVC facilitates a mine expansion through dynamic voltage support of a radial, weak grid.

Two SVCs were successfully installed to support the voltage at the Oyu Tolgoi Copper and Gold mine in Mongolia. The 220 kV mine, owned by Rio Tinto, Ivanhoe Mines and the Mongolian government is expected to produce 170.000 tonnes of ore concentrate per day. The large complex fed over a 200 km long transmission line, was in need of reactive power 100 MVA compensation to facilitate its expansion.

The majority of the loads at the site are large mining loads including several 20 MW SAG-mills and Ball mills. The SVCs were installed to support the system in case one of the 220 kV lines is switched out of service and to prevent excessive over-voltages following system load rejections.

Another primary function of the SVCs is to support the system voltage in the event of a fault in the 220 kV transmission system or in the 33 kV mining distribution system. In these situations the SVCs will inject reactive power to support the TCR TCR 5th 7th 11th system during restart of the many induction motors. Finally, 100 Mvar 100 Mvar 71 Mvar 19 Mvar 10 Mvar in case of a single phase fault, the SVC will reduce the unbalance in the system enabling a swift fault recovery. Single-line diagram of one SVC

The Oyu Tolgoi SVC in Mongolia.

ABB FACTS | Static Var Compensators for Mining 9 Application example: SVC for load balancing at a Nickel Smelter Smelters – major influencers on the power grid

An important step in the refining of many ores is a pyro- An SVC was selected as the most efficient solution to chemical process. These smelters often require special compensate the submerged arc furnaces and maintain the attention and can cause problems in terms of: power quality in the feeding grid as well as in the plant itself. The resulting benefits were: −− Voltage fluctuations and flicker −− Unbalanced operation −− Increased active power in the furnaces and increased −− Harmonics productivity −− Reduced wear of power generators and other sensitive SLN (Société Le Nickel) is operating three submerged Nickel equipment reducing maintenance costs arc furnaces in New Caledonia. The main power supply was −− Phase-wise compensation and unbalance mitigation, criti- composed of four generators and initially the furnaces were cal for furnace operating with single-phase transformers compensated by harmonic filter banks only. However, the −− Lower noise to other loads and consumers connected to unbalanced load stressed the generators and when starting to the grid, increasing equipment life-span plan for a capacity increase, SLN realized that they required a −− Harmonic reduction and Grid code compliance dynamic solution to improve the power quality.

Generator negative sequence current

SVC off SVC on 120

90 A 60

0 Time The SVC nearly eliminates the negative phase sequence current and increases the power factor. In addition, the harmonic components are significantly reduced.

The arc furnace is a cause of many power quality disturbances in the power grid. The SVC mitigates these disturbances and not only does it stabilize the grid, but it also increases the plant productivity.

10 Static Var Compensators for Mining | ABB FACTS ABB FACTS

FACTS (Flexible AC Transmission Systems) is a term representing an entire family of devices for improved use and flexibility of power systems.

The SVC is a member of ABB’s family of FACTS technologies. ABB in the mining industry, it started in 1891... Other members are: ABB delivered its first steam generator for a mine hoist in 1891. Since then, ABB has delivered a wide range of −− SVC Light®/STATCOM products for the mining industry and has mining references −− TCSC (Thyristor Controlled Series Capacitor) in more than 75 countries. ABB has been delivering SVCs −− Series Compensation for more than four decades and with more than 500 SVCs −− DynaPeaQ® energy storage installed world-wide, we are proud to be the leading company in reactive power compensation systems.

FACTS Care

ABB customer support assists you throughout all phases customers with risk management to secure a continuous of the installation lifecycle. With our FACTS Online remote operation. Select from a wide range of service options that service, ABB offers service 24/7 globally and assists our best fits your needs.

STATCOM is part of ABB‘s wide range of power quality solutions to the mining industry.

ABB FACTS | Static Var Compensators for Mining 11 Contact us

ABB FACTS SE-721 64 Västerås, Sweden Phone: +46 21 32 50 00 E-Mail: [email protected] www.abb.com/facts © Copyright 2014 ABB. All rights reserved. Specifications subject to change without notice. ABB Id No: 1JNS017471 EN 2014 © Copyright 2014 ABB. All rights reserved.