Mining site — server room and backup power
Construction of a secure technical room and its power chain, on an isolated site with no reliable public grid.
- Weeks of measurement before sizing
- 4
- Load tests per year
- 12
Reference KP-2024-008
Industrial generator sets
A generator set is sized from a load study, never from the contracted supply.
- Parent division
- Power and backup supply
The problem
Contracted supply describes a contract, not a need.
The most common method is to take the supply contracted with the distributor and order a set of similar rating. It almost always produces an oversized installation.
An oversized set runs lightly loaded, which fouls the engine, degrades combustion and shortens its life. It costs more to buy, more in civil works, and it fails sooner. An undersized set, on the other hand, collapses when a motor or a compressor starts.
Between the two, the only reliable method is the load study: list what must be backed up, separate permanent from intermittent loads, account for starting inrush and non-linear loads, then adopt a rating that leaves room for extension without installing an engine that will never work.
Backup power chain, schematic
- 01Public grid
- Normal source, whose availability cannot serve as a design assumption.
- 02Generator set
- Replacement source, sized on the load assessment and its growth allowance.
- 03Automatic transfer switch
- Switches over without human intervention, with a delayed return to the grid.
- 04Main low-voltage board
- Protection, discrimination and separation of critical and ordinary feeders.
- 05UPS
- Covers the generator start-up window, during which no source is supplying.
- 06Critical loads
- Supervision, security, servers and links whose loss is an incident.
- 07Ordinary loads
- Sheddable feeders, whose interruption carries no operational consequence.
The marked points are reported to supervision: grid presence, source state, fuel level, engine hours and load-test results.
Scope
What the service covers
- Load study
- A list of the circuits to be backed up, measured consumption where an installation exists, starting inrush, power factor, non-linear loads, and an extension margin settled with the client.
- Machine selection
- Prime and standby ratings, expected duty, canopy and acoustic treatment, and derating for site conditions — temperature, altitude, dust.
- Civil works and integration
- Base, fresh air and extract ventilation, exhaust and its route, liquid containment, access for maintenance and for replacing the machine.
- Source transfer
- Automatic transfer panel, timers, order in which outgoing circuits are restored, interlocking between sources, on-load transfer tests, and behaviour when the grid returns.
- Fuel
- Day tank and bulk tank, transfer, gauging, filtration and draining, adopted autonomy, resupply procedure and lead time, and fuel quality control.
- Operation and maintenance
- Remote monitoring, periodic on-load tests, maintenance contract, wear parts held in stock, and a register of tests and interventions.
Situations
The most frequent situations
- Remote mining or industrial site
- The grid is absent or unreliable and the set becomes the primary source. Design then turns on machine redundancy and fuel logistics.
- Administrative or hospital building
- Backed-up circuits are ranked and restoration times constrained. The set works together with uninterruptible supplies for sensitive equipment.
- Server room
- The set takes over from the batteries. Start and transfer time must stay below the UPS autonomy, with a margin proven by test.
- Network of sites
- Distributed machines, centralised monitoring, scheduled periodic tests. The point is knowing remotely which set will actually start on the day.
Requirements
What to require, of us as of anyone
These requirements hold whichever supplier is appointed. Written into a tender, they filter out the responses that will not hold.
- A written load study separating permanent loads, intermittent loads and starting inrush.
- An explicit distinction between prime and standby rating, and the duty adopted.
- The guaranteed restoration time, measured by on-load transfer test rather than declared.
- The fuel autonomy adopted, the resupply procedure and the supplier’s real lead time.
- Ventilation and exhaust arrangements, with the temperatures reached in continuous running.
- A programme of periodic on-load tests, recorded in a register.
- The list of wear parts to be held in stock, and the lead time for those that are not.
Pitfalls
Common mistakes, and what they cost
- Sizing from the contracted supply
- Contracted supply covers every use, including those that need no backup. The set that follows is oversized, more expensive and less durable.
- Running tests off load
- An off-load test confirms the engine starts. It confirms neither circuit restoration, nor behaviour under load, nor thermal behaviour. Most failures observed in real conditions would have been revealed by an on-load test.
- Neglecting fuel quality and ageing
- Stored fuel degrades and takes on water. Without filtration, draining and periodic checks, the failure occurs at start-up — the one moment the set is relied upon.
- Leaving ventilation until last
- An under-ventilated room lets temperature rise until the engine shuts down on protection. The defect does not show in a short test, but after twenty minutes of running, that is, during the first real outage.
Questions
Questions asked before consulting
How is the required rating determined?
Through a load study. The circuits to be backed up are listed, permanent loads separated from intermittent ones, starting inrush from motors and compressors accounted for, then power factor and non-linear loads. An extension margin settled with the client is added last. The adopted rating is the result of that calculation, never a copy of the contracted supply.
How much fuel autonomy should be planned?
It follows from the real resupply lead time at the site plus a margin, not from a standard figure. An urban site resupplied within hours and a remote site resupplied over several days do not call for the same storage. Day tank and bulk tank are sized together, with their containment.
How often should a set be tested?
A periodic on-load test at a regular interval, recorded in a register. Off-load testing has limited value: it reveals a starting fault, not a capacity fault. The interval is set with the manufacturer and the operator, according to how critical the site is.
Two sets rather than one?
Redundancy is justified when a site outage costs more than the second machine, or when no maintenance window exists. Two machines allow one to be serviced while the other carries the load, which a single machine forbids. The question is settled on acceptable downtime, not on capital budget.
How does the set work with the UPS?
Batteries carry the load during detection, starting and transfer. That time must stay well below UPS autonomy, and the margin is verified by test rather than from datasheets. Insufficient battery autonomy cancels the benefit of the set for sensitive equipment.
Can a set be monitored remotely?
Yes, and it becomes necessary as soon as there are several sites. Monitoring reports machine status, fuel level, faults and test results. It turns a declared check into verifiable information, which changes how a distributed fleet is run.
Evidence
Where we have applied it
Regional operator — core network modernisation
Replacement of the core network and backup power at fourteen points of presence, with no commercial service outage.
- Points of presence migrated
- 14
- Longest outage window observed
- 4 min
Reference KP-2023-021
European diplomatic mission — multi-system security
Complete overhaul of access control, video surveillance and backup power for a chancery in service.
- Systems merged
- 3
- Service interruptions
- 0
Reference KP-2022-014
Neighbouring subjects
Solutions concerned
Consultations · Pre-qualifications · Partnerships
Let us discuss the actual case.
Describe the site, the dominant constraint and the deadline. We will say what requires a preliminary study and what can be committed directly.