Overload Relays & Power Controllers for Cement Industry Load Management

When Your Maximum Demand Charge Costs More Than Your Energy Bill

Here is a question every electrical engineer managing a cement plant or building materials facility eventually confronts: why does the electricity bill show a demand charge that dwarfs the actual energy consumption charge — even during months when production was moderate? The answer lies in a single 15-minute interval of peak coincident demand that your distribution utility recorded and billed at a penalising tariff slab. In cement and building materials manufacturing, where kilns, ball mills, crushers, conveyors, compressors and lighting panels all compete for current simultaneously, unmanaged peak demand is not an occasional nuisance — it is a structural cost embedded in every invoice.

This article is not about generic energy audits or theoretical power factor theory. It is a panel-level engineering guide to how three specific Novatek Electro devices — the OM-310 Demand Controller Overcurrent-Earth Fault Relay, the OM-163 Power Controller and Current-Voltage Monitoring Relay, and the RMT-101 Single Phase Digital Overcurrent Relay — are used by panel builders and electrical contractors to implement working demand-side management schemes inside MCC panels and distribution boards for cement and building materials applications.

Why Peak Demand Becomes an Engineering Problem in Cement & Building Materials

The Nature of the Load

Cement and building materials production is characterised by high-inertia motor loads — ball mills, raw material crushers, rotary kilns, clinker cooler fans, bucket elevators and screw conveyors — that draw heavy starting currents and sustain large running currents for extended periods. These loads are often started in sequence but, under production pressure, are frequently all energised simultaneously. Add compressor banks, dust collector blower motors, lighting circuits and office HVAC, and the aggregate demand at the main incomer regularly spikes well above the contracted maximum demand (CMD) limit.

The Electrical Engineering Reason Demand Spikes Occur

Most Indian industrial tariffs are structured under two-part billing: an energy charge (Rs/kWh) and a maximum demand charge (Rs/kVA or Rs/kW per month, billed on the highest recorded 15-minute or 30-minute block). If demand exceeds the contracted level, the utility bills at a significantly higher rate — sometimes applying a penalty multiplier. The root electrical cause is the absence of automatic load coordination: nothing at panel level monitors aggregate power draw in real time and sheds lower-priority loads before the demand meter records the peak. Manual discipline among operators is unreliable, especially during shift changes or startup sequences after a power interruption. The result is that non-critical loads — lighting, small ventilation fans, auxiliary pumps, battery chargers — remain energised during the exact window when production motors are at peak draw, pushing the 15-minute average over the CMD threshold.

A secondary electrical problem compounds this: poor power factor on motor-heavy loads pushes kVA demand higher than kW demand, increasing the billing base. Overloaded circuits that trip thermal relays interrupt production unexpectedly, costing more than the energy saved. The engineering solution must therefore address three things simultaneously: real-time power monitoring, automatic contactor-level load shedding, and reliable overcurrent protection.

The Novatek Electro Solution: Three Devices, One Coordinated Scheme

OM-310 — The Master Demand Controller (3-Phase, Up to 800 A / 450 kW)

The OM-310 is a numeric, multi-functional demand controller and overcurrent-earth fault relay designed for 380–415 V three-phase or four-pole systems. It covers a current range of 5 A to 800 A, corresponding to motor and load ratings from 2.5 kW to 450 kW — essentially covering everything from a small auxiliary pump to a large kiln drive within a single relay platform.

Demand control logic: The OM-310 performs continuous power monitoring and compares real-time consumption against two programmable thresholds. When power consumption exceeds the main threshold for a user-set time, it executes complete load rejection on the assigned contactor output. When consumption reaches an intermediate level, it executes partial load rejection — shedding a configured subset of non-critical loads while keeping priority circuits live. This two-level response is critical in cement plants where some auxiliary circuits (instrument air compressors, seal water pumps) cannot be interrupted even briefly.

Protection functions: Overcurrent protection, earth leakage protection, and voltage monitoring are integrated. The output is potential-free: a programmable 1 × SPDT (1NO + 1NC) contact for signalling or alarm, and a power output 1 × DPDT (2NO + 2NC) for direct contactor driving. The dual LED display gives operators real-time current and power readings without external metering.

Price: Rs.15,687 per piece (ex-GST)

OM-163 — Single-Phase Power Limiter and Monitoring Relay (Up to 63 A)

The OM-163 is a digital automatic power controller and current-voltage monitoring relay for single-phase circuits, rated for 130–300 V AC and up to 63 A at 250 V AC. In a cement plant distribution scheme, single-phase circuits feed lighting panels, small ventilation units, office equipment, site CCTV, and building management loads — exactly the category of non-critical loads that should be shed first during a peak demand event.

The OM-163 combines four functions in one DIN-rail unit: power controller (limiter), voltage monitoring, energy metering, and overcurrent relay. The 3-digit display provides operators with immediate feedback on measured current, voltage, and energy consumption. Because it monitors voltage as well as current, the OM-163 can also protect sensitive control equipment from voltage sags that commonly accompany heavy motor starting events on a weak bus — a real problem in building materials plants served by rural or semi-urban feeders with high source impedance.

Price: Rs.3,500 per piece (ex-GST)

RMT-101 — Digital Overcurrent Relay with Built-In CT (0–100 A)

The RMT-101 is a single-phase digital overcurrent relay with a built-in current transformer, covering a fully settable range of 0–100 A on a 220–240 V supply. Its SPDT potential-free output (1NO + 1NC, rated 8 A) drives any standard contactor or shunt trip coil, making it straightforward to integrate into existing MCC panels without rewiring. The latching coil type ensures that once a load-shed command is issued, the contactor remains open even if relay power is momentarily interrupted — an important safety behaviour in panel-level load management schemes.

The RMT-101 is the right choice for individual circuit-level overload protection and load-rejection in the single-phase distribution branches feeding auxiliary equipment: dust collector bag-filter motors, small conveyor belt drives, silo aeration blowers, and similar loads in the 0–100 A range. The nominal insulation voltage of 450 V and rated impulse withstand voltage of 2.5 kV confirm suitability for standard industrial distribution environments. Protection degree is IP40 for the device body and IP10 at terminal blocks, consistent with panel-mounted installation in a standard enclosure.

Price: Rs.5,475 per piece (ex-GST)

Technical Specifications at a Glance

Quick Selection Guide for Cement & Building Materials Applications

Where These Devices Are Used in Cement & Building Materials

• Cement grinding and blending plant MCCs: OM-310 on main incomers for demand control; RMT-101 on individual feeder branches for auxiliary motor overload protection.
• Ready-mix concrete batching plant electrical panels: OM-163 for single-phase ancillary load limiting; RMT-101 for mixer motor branch protection.
• Brick and tile kiln electrical distribution boards: OM-310 for three-phase kiln drive demand management and earth fault monitoring.
• Fly ash handling and silo discharge systems: RMT-101 on aeration blower circuits; OM-310 on the combined silo panel incomer.
• Building materials warehouse and dispatch areas: OM-163 on lighting distribution boards for automated non-critical load shedding.
• DG set paralleling and changeover panels: OM-310 for generator overcurrent protection and demand limit enforcement on DG supply.
• Aggregate crushing and screening plants: OM-310 for overall plant demand monitoring; RMT-101 for individual screen drive overload protection.

Why Novatek Electro?

• ISO 9001:2015 certified manufacturer: Quality management system certification covering design, manufacturing and supply of electrical protection relays — not just a trader importing and relabelling.
• CE certified products: OM-310, OM-163 and RMT-101 all appear on Novatek Electro India's CE Declaration of Conformity (Annexure-1), confirming compliance with relevant EU low-voltage and EMC directives — a baseline assurance of electrical safety and electromagnetic compatibility.
• Made in India: Designed and manufactured in India, with domestic supply chains that support faster lead times and local after-sales service — critical for cement and building materials plants that cannot sustain extended equipment downtime.
• 30+ years of product development experience: Novatek Electro's parent organisation has over three decades of specialisation in electrical protection relays, monitoring devices and power management equipment.
• Full after-sales support: Technical documentation, connection diagrams, and application support are available through authorised distributors and the Intelli-Electro online channel — accessible to panel builders and site engineers across India.

Frequently Asked Questions