For mining power systems the strongest static VAR generator (SVG) is an IGBT voltage-source-converter unit that delivers stepless reactive current in under 10 ms, runs bidirectionally (inductive and capacitive), and scales in parallel from tens of kVAr to several MVAr per switchboard bay [S5][S7].
Mining sites are dominated by ball mills, crushers, conveyors, hoists, ventilation and pumping loads driven through variable-frequency drives (VFDs) and soft starters, which together create low power factor, voltage flicker, and 5th/7th/11th/13th harmonic currents, and these are the exact disturbances an SVG is specified to neutralise [S1][S2].
Why Mining Loads Force a Switch from Capacitor Banks and SVCs to SVG
Underground coal and hard-rock mines with thyristor-controlled hoisting machines inject non-characteristic harmonics, including triple-n (3rd, 9th, 15th) and interharmonics, because the firing angle is not synchronised cleanly at the voltage zero crossing, and these currents can overheat the neutral and trip unfiltered capacitor banks [S1].
Classic SVCs using thyristor-controlled reactors (TCR) plus thyristor-switched capacitors (TSC) correct the fundamental reactive power but still draw harmonic current from the thyristor bridge itself, so an SVC is not a drop-in replacement where a modern VFD-dense mine has already raised the background THDi above 8-10% [S1][S5].
Fixed or stepped capacitor banks correct only capacitive (leading) reactive power, cannot absorb inductive vars, and at low voltage simply de-rate, which is exactly the wrong behaviour for a mine feeder sagging to 0.85 pu during a crusher start [S5].
Core Specification Targets for a Mining-Grade SVG
Response time under 10 ms (full step from capacitive to inductive) is the headline number, and SinaVa's published spec sheet quotes "less than 10 ms" overall, which is what separates an SVG from a 200-500 ms SVC [S5].
The compensation must be stepless and bidirectional: the same IGBT bridge that supplies capacitive current during motor starting must absorb inductive vars when the conveyor line goes light, and target power factor is adjustable in both leading and lagging quadrants [S5].
Modular parallel architecture is non-negotiable for a mine: cabinets rated 50 kVAr, 100 kVAr, and 200 kVAr are stacked to a common DC bus, so a 1500 kVAr pit-top substation can be built from seven 200 kVAr modules plus one spare, and a single module failure drops only 7-15% of compensation rather than the whole bank [S3][S5].
Rated voltage typically 380-480 V low-voltage or 6 kV / 10 kV medium-voltage; SVG cabinets at 400 V are the standard building block for surface crushers and conveyor MCCs, while 6-10 kV SVG-STATCOM skids serve pit-top and underground main substations [S3][S6].
SVG vs SVC vs Capacitor Bank: Decision Matrix
Unlike SVGs, which provide stepless compensation in milliseconds, conventional capacitor banks operate through fixed compensation steps [S5].
SVCs (TCR + TSC) add dynamic range and inductive absorption but inject their own characteristic harmonics (5th, 7th, 11th, 13th) and need harmonic filters, taking 200-500 ms to settle, which still lets crusher-start flicker through [S1][S5].
SVGs (IGBT VSC) deliver sub-10 ms, stepless, bidirectional compensation and act as an active harmonic filter when firmware is enabled, which is why the same IGBT cabinet is often sold as "SVG + APF" in mining catalogues [S2][S5].
Where an SVG Earns its Place in a Mining Network
On a thyristor-controlled mine hoist, the worst flicker event is the acceleration ramp; an SVG sized at 30-50% of the hoist's MVA rating holds the point-of-common-coupling voltage inside the ±5% flicker limit (Pst < 1.0) that most utilities enforce, and has been demonstrated in underground coal hoisting applications [S1].
On a crusher/conveyor line fed by long 6 kV cable, the SVG sits at the pit-top substation and corrects the leading power factor that arises when the conveyor runs empty and the cable capacitance dominates, a regime where a capacitor bank would push the bus into over-voltage and trip [S2][S7].
On a mill with twin 4 MW slip-ring induction motors, paralleling 200 kVAr SVG modules at the 480 V MCC bus raises displacement power factor from 0.78 to a settable 0.95-0.99 and removes the utility reactive-power penalty, which at industrial tariff rates typically pays back the SVG inside 12-24 months [S2][S3].
Sizing Rules That Actually Work on Site
Step one is the load audit: log active power P (kW), apparent power S (kVA), and displacement power factor cos φ1 on the main incomer for at least 7 days, including one start of the largest motor, then compute required compensation Qc = P × (tan φ1 - tan φ_target) [S2][S5].
Step two is the headroom: in a mine with frequent crusher or hoist starts, oversize the SVG by 25-40% above the steady-state Qc, because the unit must hold cos φ on target through the transient, not just at the average operating point [S2].
Step three is the harmonic option: if the existing THDi at the PCC is above the IEEE 519 5% limit for voltage, specify the same IGBT cabinet in active-power-filter (APF) mode and allocate 30-50% of its kVA rating to harmonic cancellation, since the 5th, 7th, 11th and 13th harmonics from a VFD cluster are predictable and selectively cancellable [S1][S2].
Failure Modes, Limits, and What SVG Will Not Fix
An SVG cannot create active power, so a mine with a true under-frequency or under-kW shortage still needs a real generator or BESS, not an SVG; reactive compensation only moves the point on the P-Q circle, it does not expand it [S7].
In a weak radial feeder with source impedance above 15-20%, the SVG's IGBT current limit becomes the binding constraint and the controller will simply hit ceiling during the worst 100-300 ms of a motor start, so a soft-starter or VFD ramp on the load motor is the complementary fix [S1][S5].
Ambient rating matters: surface pit-top cabinets are typically rated 0-40 °C with derating above 1000 m, while underground units need IP54, dust-ingress protection, and an ambient ceiling closer to 35 °C because drift temperatures are higher, so the published kVAr nameplate must be de-rated by 1-2% per 100 m above 1000 m [S3].
Trackable Signals and Sourcing Standards
Two signals to watch between now and the next tender cycle: (1) the publication of IEC TR 61800-5-1 application guidance for active front-end and SVG equipment in mining, which several working groups have been drafting, and (2) the EN 50160 / IEEE 519 enforcement trend on voltage flicker Pst at pit-top PCCs, where utilities have started to issue flicker-based curtailment notices to mines with hoists older than 15 years [S1][S2].
For a deeper walkthrough of how SVG sizing maps to specific load lists, see the Static VAR Generator selection map, and for the safety-instrumentation side that travels with the same switchboard see the combustible-gas detector spec map for mining. For an overview of the device class itself, the static var generator encyclopedia entry collects the canonical definitions.
For component-level specifications, see mining dump truck, and function generator.