District heating and cooling networks
Leakage wire monitoring
Together, the leakage wire, the measuring module and the alarm limits show whether there is moisture in the pipe insulation and where it comes from.
Principle
How the monitoring works
Two copper leakage wires (Nordic system, 1.5 mm²) run in the insulation of a pre-insulated district heating or district cooling pipe. The wires form a loop that the Pipeguard module measures automatically.
The module detects a moisture spread of just a few centimetres around the leakage wire over about 8 km of wire, or 4 km of pipe. It detects both leaks from inside the pipe and water entering the insulation from outside through the casing pipe.
Readings and alarms are shown in the monitoring system. A Fixbox measuring point makes handheld measurements easy and gives a stable earth point.
AI generatedMeasurement methods
Loop resistance
0–100 Ω
Shows whether the loop is intact. If the leakage wire breaks, the module measures the wires from both directions and monitoring continues.
Insulation resistance
0–10 000 kΩ
Resistance between the leakage wire and the steel pipe. Above 10 000 kΩ in an intact pipe; moisture in the insulation lowers the value.
Galvanic voltage
0–1000 mV
0 mV in an intact pipe. The voltage tells whether the water is district heating water or comes from outside.
TDR measurement (pulsPG)
8000 m
Compares the TDR curve with the reference curve and, in case of damage, gives the distance to the fault.
Interpreting the readings
| Situation | Insulation resistance | Galvanic voltage |
|---|---|---|
| Intact pipe | above 10 000 kΩ | 0 mV |
| Joint or casing leak (groundwater from outside) | falls | rises clearly more than with district heating water |
| Leak from the district heating pipe into the insulation (district heating water) | falls | rises, but less than with water from outside |
| Short circuit | short circuit starts at 1–5 kΩ, finally 0 | falls to zero |
Alarm levels
The QPG summary alarm
QPG combines insulation resistance and galvanic voltage into one grade on a scale of 0–5. Find the insulation resistance level (row) and the galvanic voltage level (column). Each alarm limit passed raises the grade by one.
| Insulation resistance ↓ / Galv. voltage → | Normal | High | High high |
|---|---|---|---|
| Normal | QPG 0 | QPG 1 | QPG 2 |
| Low | QPG 1 | QPG 2 | QPG 3 |
| LowLow | QPG 2 | QPG 3 | QPG 4 |
| Short circuit (1–5 kΩ) | QPG 5 | QPG 5 | QPG 5 |
- Overriding rule: when insulation resistance falls to the short-circuit level (1–5 kΩ), QPG is always 5 regardless of galvanic voltage.
- QPG 1 is an early stage: one value has passed the first alarm limit.
- QPG 5 means a short circuit: the values cannot fall any lower, and damage to the pipe has certainly started.
Recommended limits
| Level | Value | Meaning |
|---|---|---|
| Normal | above 10 000 kΩ | Dry insulation. The value of a new, intact pipe. |
| Low (1st limit) | 200–500 kΩ | Early sign of moisture. |
| LowLow (2nd limit) | about 50 kΩ | The insulation has clearly deteriorated. |
| Short circuit | 1–5 kΩ | Below this level the loop is short-circuited. QPG always goes to 5. |
| Level | Value | Meaning |
|---|---|---|
| Normal | about 0 mV | Intact pipe, no water in the insulation. |
| High (1st limit) | about 50 mV | Deviation detected. |
| High high (2nd limit) | about 200 mV | Clear rise in voltage. |
Limits are set per loop in the monitoring system. In new networks in good condition the Low limit can be set very high, e.g. 9 900 kΩ, so that deviations are detected as early as possible.
Installation, power and communication
Secure communication
The module’s SIM card is in a private APN, and all traffic runs in a VPN tunnel directly to the operator’s servers. A SIM card taken out of the module cannot connect to anything but Pipeguard modules. The same connection allows remote support and module updates.
Power supply
The microPG and miniPG tell from their supply voltage whether they run on battery or mains. On battery the module works in energy-saving mode; above 14.2 V it stays online all the time. A solar panel connects through a regulator, and a solar power tower is also available, with an optional 12 V fan to ventilate the chamber.
Location
If the signal is weak in the chamber or substation, the antenna is taken outside. Metal structures can block the connection completely, so test the place before installing permanently. At least two level switches can be connected to the modules.
Which module suits your network?
See which module suits your network, or request a quote.