These safety recommendations and requirements apply to the following capacitors and standards. Their purpose is to describe the state of technology that must, as a rule, be adhered to in all relevant contracts for goods and services. Misapplication, such as exceeding the design limits, use for applications different from those indicated in the catalogue or use for applications inappropriate for the characteristics of the type of capacitor used, may fail the capacitor or expulsion the capacitor element from the case. Normal end-of-life failure is characterised by a loss of capacitance, increased dissipation, and/or permanent open circuits. Therefore, the user is cautioned to provide whatever additional protection or enclosure is necessary to avoid possible damage or injury in case of failure. BJEPL disclaims any responsibility for damages to objects and people originated by improper use of its products.

Since capacitors are electrical energy storage devices, they must always be handled with caution. Even after being turned off for a relatively long period, they can still be charged with potentially lethal high voltages.
The same applies to all system components and devices which have an electrically conductive connection to the capacitor. The general rules of good electrical engineering practice must always be complied with when handling live components in electrical systems.

The manufacturer’s installation, application and maintenance instructions and the relevant standards must always be complied with.

• Capacitors must never be stored or used outside the specified temperature ranges.
• Capacitors may not be stored or operated in corrosive atmospheres, particularly not when chlorides, sulphides, acids, alkalis, salts, organic solvents or similar substances are present.
• In dust and dirt-prone environments, regular checks and maintenance (particularly of the terminals and insulators) are necessary to prevent the creation of creepage distances between live parts and/or to the protective conductor/ground.
• The maximum temperatures (including inherent heat), voltages, currents, power, thermal resistances, frequencies, discharge times and switching frequencies specified in the datasheet must be adhered to.
• A means of enough dissipation for heat (fan, cooling) or escaping gases/liquids must be provided in case of a malfunction. Required minimum distances (e.g. to sources of heat) must be maintained.
• Specified torques for electrical connections and fasteners must be adhered to.
• Mechanically or electrically damaged, leaky, or otherwise damaged capacitors may not be used or continue to be used.
• Existing protective devices of the capacitors should not be manipulated, removed or impaired in their function.

• Internal protective devices offer essential protection against specific internal faults, ageing and overload.
• Internal protective devices alone are not enough to prevent all conceivable dangers in case of malfunction. The so-called self-healing capability is not the same as fail-safe system stability.
• Most internal protective devices can interrupt the voltage only within the capacitor. They do not fuse in the classical sense, such as cable or device fuses which interrupt the voltage upstream from the faulty system component.
• It is advisable to supplement internal protective devices with external protective devices, for example:
1. short-circuit protection by fuses or circuit breakers/protective relays
2. overload protection for fundamental frequency and harmonics using current measurement
3. load unbalance protection
4. temperature control
• Depending on their protective mechanism, protective devices are subject to technical and functional limits, which will inevitably cause malfunctions when exceeded.
• Such violations include excess temperature, overvoltage, incorrect application, incorrect installation, faulty maintenance, mechanical damage, or operation outside the specification’s technical limits.

The most frequent risk factors which cause capacitor damage and possibly also the failure of the internal protective devices are:

• Exceeding the permissible temperature on the capacitor surface (every increase in operating temperature of 7 K cuts life expectancy in half).
• Overvoltage’s, overcurrent and high inrush currents even if they only occur briefly or cyclically (a continuous increase in the capacitor’s operating voltage of 8 % cuts life expectancy in half).
• Network harmonics, resonances created by harmonics or flicker even when they occur only briefly or cyclically.
• Ageing of the lighting equipment and consequential excess temperature or high UV stress.
• Failure of other components in a common circuit and consequential overvoltages or overcurrents.
• Interaction with other reactive power components and parasitic capacitances (cable) or inductivities in common circuits.
• Even if the test based on the capacitor standard is passed, this does not ensure comprehensive protection against all possible overloading.

(Currently, several customers are requesting special tests on unprotected capacitors with extreme overvoltage’s and temperatures to prove safe capacitor performance.)
(These additional tests on self-healing PEC capacitors without a safety system (unprotected) are often referred to as “destruction tests” and are not IEC compliant. Furthermore, such tests are unsuitable for evaluating potential risks posed by PEC capacitors or their behaviour in the event of a fault.)
(Instead of these tests, critical operating conditions that could lead to a PEC capacitor’s failure (voltage/current/temperature) should be monitored within the application.)

• During the operation of thyristor-switched capacitor systems, high DC voltages can occur continuously on the capacitors of compensation systems that are not switched on. These DC voltages must be considered when designing the capacitors and their discharge devices.

• Power capacitors can be a significant risk of failure due to their stored energy and/or properties during operation in networks with high short circuit power. For example, the use of ever-larger capacitors in multi-level high-voltage direct current (HVDC) transmission systems, which are notable for the size, arrangement, and number of capacitors, poses risks.
• If energy values exceed 30 kJ per capacitor unit, it is assumed that the risk will increase if there is an uncontrolled release of this energy in the event of failure. This poses an additional hazard potential in systems containing several capacitor units due to possible avalanche effects.
• Power capacitors can actively fail when internal or external protective devices are missing, incorrectly dimensioned, or failed. They can burst, burn or, in extreme cases, explode. This also applies to gases escaping from internal protective devices (overpressure valve).
• The gases (e.g., hydrocarbons as decomposition products of the organic insulating materials used) released in case of damage are flammable and can create explosive mixtures. The fire load of a power capacitor is approx. 40 MJ/kg. In this context, it is to be noted that – depending on size – combustible materials make up around 55 % of the total mass of small capacitors and max.75 % of large capacitors.

• The capacitor manufacturer cannot predict all stresses that a power capacitor can be subjected to and considered in the design. This means that the user bears crucial co-responsibility here. For this reason alone, safety and quality should be the top priorities when a capacitor is selected. Therefore, we urgently recommend the use of capacitors with appropriate internal protective devices.
• Before designing the application, capacitors must be checked for their suitability for this application. All influences (parameters) must be considered. Unexamined use in an application may have serious consequences.
• Particularly with sensitive applications, the capacitors’ internal protective devices must be supplemented by the user with suitable external protective measures. External protective measures are even mandatory when capacitors are used without internal protective devices.
• When power capacitors are used, suitable measures must always be taken to eliminate possible danger to humans, animals, and property during operation or when a failure occurs. This applies to capacitors both with and without protective devices. Regular inspection and maintenance by a competent person are, therefore, essential.
• Power capacitor manufacturers who are members of the ZVEI will gladly advise users who plan an application, provide firm recommendations and offer their services.