Surge Protection for Electrical Systems in Buildings (IEC 60364, DIN VDE0100)


Surge Protection for Electrical Systems in Buildings (IEC 60364, DIN VDE0100)

IEC/TC 64 provides detailed treatment methods for building surge protection. The corresponding international standard IEC 60364 is given in Chapter 44 of this publication. The relevant chapters in the (German) national standard series DIN VDE 0100 are from Part 440.

Chapter 44 of IEC/TC 64 is divided into:

Chapter 44 Protection in Case of Surge

Introduction to Section 441

Section 442. Low voltage system protection in case of ground fault of high voltage system

Section 443 Atmospheric overvoltage protection

Section 444 Protection against Electromagnetic Interference in building systems

1. Part 443 of IEC 60364-4-443/DIN VDE 0100

Current IEC 60364-4-443(text 1995-04) "Publication 364: Electrical Installations in Buildings; Part 4: Safety protection; Chapter 44: Overvoltage protection; Section 443: Atmospheric overvoltage protection "or DIN VDE 0100 Section 443 has the following statement:

"These standard requirements are proposed to describe measures to limit transient overvoltages, with the aim of reducing the risk of failure of the system and the equipment to which it is connected to to an acceptable level, and the procedures are in accordance with the insulation fit principles in the IEC 664 publication 'Insulation Fit for Low Voltage Systems and Equipment'.

"The purpose of the overvoltage category is to distinguish between high and low equipment availability. The availability of equipment varies with demand, which is related to the continuity of operation of the equipment and the acceptable risk of failure, damage and failure. The system can only be properly insulated if the equipment is properly surge resistant. Proper insulation will reduce the risk of failure/failure to acceptable levels/limits. This is the basis of the surge protection rules.

"A higher overvoltage category means that the device is inherently more surge resistant and that there are more surge control/protection options available."

In the above standards, lightning environmental conditions AQ1 to AQ3 are defined and the application of surge arresters depends on these environmental conditions. The classification of lightning effect is as follows:

AQ3: Direct effects of lightning (IEC 61024-1);

AQ2: Indirect effects of lightning, hazards from power supply systems;

AQ1: Negligible lightning effect.

2. IEC 60664-1/DIN VDE 0110, Part 1

IEC 60664-1 "Insulation fit for Equipment in Low-voltage systems - Part 1: Principles, requirements and Tests" came into force in 1992, and the corresponding part in Germany is DIN VDE 0110-1(VDE 0110 Part 1):1997-04(IEC 60664-1:1992, Revised edition). This standard details the insulation fit of equipment in low voltage systems. This standard applies to devices with rated AC voltage less than 1000V, rated frequency less than 30kHz, or rated DC voltage less than 1500V.

The standard has the following definitions:

1) Insulation coordination: Taking into account the expected microenvironmental conditions and other important external functions, the insulation characteristics of electrical equipment should be graded accordingly.

2) Surge tolerance voltage: the maximum surge voltage with conventional waveform and polarity that will not cause insulation breakdown or flashover under given conditions.

3) Rated surge voltage: The surge voltage value marked by the manufacturer for the equipment or part of the equipment, indicating the specific resistance of the insulation to multiple peak voltages.

4) Overvoltage category: a numerical value indicating surge voltage tolerance (Note: Overvoltage category is indicated by I, , and ).

5) Finite overvoltage state: A state in an electrical system in which the expected transient overvoltage is kept within a limited range.

In this standard, the principle of "insulation coordination" is as follows: Insulation coordination includes the consideration of the application conditions of the equipment and the surrounding environment, and the selection of the electrical insulation characteristics of the equipment. To achieve an insulating fit, the rating of the equipment must be determined on the basis of the voltage it will be subjected to during its likely lifetime.

With respect to transient overvoltages, the standard states that the insulation fit with respect to transient overvoltages is based on the state in which the overvoltage is restricted. There are two kinds of restrictions:

System restrictions. A state in an electrical system in which, due to the characteristics of the system, the expected transient overvoltage can be assumed to remain within a limited range.

Protective restrictions. A state in an electrical system in which the expected transient overvoltage can be assumed to be confined to a given range due to the application of a special overvoltage limiting method.

Note 1 Overvoltages in large complex systems, such as low voltage systems, which are subject to multiple and variable effects, can only be judged statistically. This is particularly true for atmospheric overvoltage whether the limitation is achieved by an in-system limitation or by a protective limitation.

Note 2: It is recommended to check the probability of overvoltage according to whether there is a system limit or whether there is a required protective limit. This inspection requires information on electrical system data, thunderstorm day level and amplitude of transient overvoltage (this inspection procedure is used in IEC60364-4-443 for power supply systems connected to low voltage systems within buildings).

Note 3 Special overvoltage limiting methods may contain elements that store or deflate energy and safely deflate the energy of the expected overvoltage at the installation point.

To apply the principle of insulating fit, two different types of transient overvoltage must be considered:

Transient overvoltage originating in the system where the device resides (to which the device is connected through its terminals).

Transient overvoltage originating from the device itself.

This foundational safety standard explains to the technical committee (that is, those responsible for the standardization of various devices) how insulation fits together. In order to make the specification of the equipment consistent with the insulation fit requirements, these technical committees must specify the overvoltage class of the equipment according to the possible application of the equipment, taking into account the parameters of the system to which the equipment is to be connected.

The overvoltage category is a way of keeping equipment operating to basic requirements and differentiating the availability of equipment by possible risk of failure. The specific value of the equipment "surge withstand voltage" and the overvoltage class together enable the whole device to be reasonably insulated. The surge withstand voltage value and overvoltage category are the basis for limiting overvoltage and reducing the failure risk to an acceptable value. The higher the overvoltage category, the better the surge tolerance of the device, and the wider the range of surge limiting methods.

The principle of the overvoltage category applies to devices that are directly powered by a low voltage system. The application of the overvoltage category is based on the surge protection requirements of IEC 60364-4-443 (note: atmospheric overvoltage is not normally attenuated in the device). The examination shows that the probability-oriented concept described below is appropriate:

For directly supplied system equipment, the overvoltage category must be determined on the basis of the following general principles:

Equipment of overvoltage class I is equipment intended to be connected to a fixed electrical installation of a building. In order to reduce the transient overvoltage to the corresponding value, in addition to the equipment protection measures already taken, some protection measures must be taken within or between the fixtures.

Equipment of class overvoltage is equipment intended to be connected to fixed installations of the building (e.g. household appliances, portable tools, and similar load equipment).

The equipment of the overvoltage category is part of the fixed device and other equipment that is expected to have high availability [such as power distribution board, circuit breaker, power distribution equipment in the fixed device (IEV826-06-01, including cable, bus, distribution cabinet, switch and power socket), industrial equipment, and other equipment (such as the fixed motor permanently connected with the fixed device)].

Equipment in the overvoltage category is equipment intended for use at and near the supply end of the building's electrical installations and in the direction of the main distribution to the system (e.g. electricity meters, overcurrent breakers and pulsation control units).

The surge voltage rating of the equipment is given based on the identified overvoltage class and the rated voltage of the equipment (note that different overvoltage classes can be applied for equipment with a specific surge voltage rating and multiple voltage ratings).

For equipment capable of generating an overvoltage at the equipment terminal (such as switchgear), the rated surge voltage means that the overvoltage generated by the equipment must not exceed this value, assuming that the equipment is operating in accordance with the appropriate standards and manufacturer's instructions (note that there is always a residual risk of generating an overvoltage beyond the rated surge voltage value, which is related to circuit conditions).

As long as surge limits are strengthened, the equipment is allowed to operate under higher overvoltage category conditions. Appropriate surge attenuation can be achieved by:

Surge protection;

Transformers with isolating windings;

Distribution systems with a large number of branches (energy that can drain surges);

capacitors that can be charged by surge energy;

Resistance or similar damping element capable of discharging surge energy.

It should be considered that each surge protection device or device in the system will release more energy than each surge protection device or device in the system if the operating voltage of the surge protection device or device at the system connection point is higher than the operating voltage of each surge protection device or device in the system connection point.


3.IEC 60364-5-534/DIN VDE 0100, Part 534

During the preparation of this book (beginning January 1997), both draft standards were available:

DIN IEC 64/867/CDV(VDE 0100 Part 534):1996-10 "Electrical Installations in buildings - Selection and installation of electrical equipment - Switchgear and control equipment - overvoltage protection equipment (IEC 64/867/CDV:1996)";

E DIN VDE 0100-534/A1(VDE 0100 Part 534/A1):1996-10 "Electrical installations in buildings -- selection and installation of electrical equipment -- Switchgear and control equipment -- overvoltage protection devices -- Amendment A1(Application to European Standard).

The draft IEC standard mentioned above has now been rejected by DKE's sub-committee UK221.3, the "Protective Measures" sub-committee. The reason is that its goals are no longer relevant to the current state of the art and therefore do not help with surge protection.

The main reason for the rejection was the fact that surge protection must take into account not only switching operations and distant lightning strikes (IEC 61024/61312-1), but also near or direct lightning interference (IEC 61024/61312-1). It is therefore necessary to establish uniform standards that take into account not only the selection and installation of lightning protection arresters, but also surge protection.

It is now accepted in engineering that complex lightning/surge protection systems require more than just a lightning arrester.

Considering this need, three types of arresters (classes I, , ) with different protection capabilities have been standardized in the relevant product standard DIN IEC SC 37A/44/CDV(VDE 0675 Part 6 A1). The concept of multiple levels of protection achieved through these different types of arresters includes not only surge protection but also protection against direct lightning strikes.

The second draft standard prepared by UK 221.3 Germany applies to further refine the above IEC text. The main section of the recommendation, section 534, discusses, on the one hand, the selection and installation of surge protection equipment due to indirect lightning strikes and switching operations in accordance with IEC 603644-443 [according to VDE 0100-443(VDE 0100 Part 443)], On the other hand, in accordance with IEC 61024-1 and IEC 61312-1, the selection and installation of protective equipment for lightning currents and surges caused by direct lightning strikes and lightning strikes near buildings are discussed.

Thus, in a major section of the standard for low voltage system installations, specifications for the selection and installation of protective devices and their compatibility with the protection measures against shock applied within the system are given. However, these draft standards are outside the scope of this book and are therefore not considered further. Nevertheless, the draft German standard is referred to in describing the various application possibilities of arresters in power supply systems.

4.3 Surge Protection of Telecommunication Systems (DINVDE 0800, DIN VDE0845)

For this information see DIN VDE 0800 Part 1 :1989-05 "Telecommunications - General concepts, requirements and tests for the safety of Facilities and Installations". The scope of application of the VDE specification includes the safety of installations and devices of telecommunications engineering (hereinafter referred to as telecommunication systems and telecommunication equipment), taking into account the prevention of risks to life, health (human and animal) or property. The standard also applies to the security of information or data processing systems where no other standards apply.

DIN VDE 0800 Part 2: "Telecommunication, grounding and equipotential connections" in 1985-07 discusses the treatment of "line shielding" (i.e. shielding made of conductive material, associated with a wire in a certain geometry) and the integration of steel structures or rebar, as cited below:

In this text, a line shield used as an electromagnetic shield (in accordance with DIN IEC 60050 Part 151 :1983-12, Section 151-01-16) can also be used as an equipotential connection because both ends are connected to the reference potential.

The steel structure and rebar are integrated into the grounding system. If the function of the building is considered to be particularly demanding for the grounding system, measures should be taken to integrate the steel structure and rebar into the grounding system in order to avoid potential differences between different points of the building and the resulting equalization of current. If the reinforcement is continuously connected, the reinforcement shall be connected to the ground bus for this purpose.


The equalizing current in the steel bar is parallel to the equipotential connecting conductor between different potential points. This current can cause interference in the telecommunication system if it is caused by undue impedance resulting in undesirable coupling with the telecommunication circuit or fluctuations in the contact resistance. Continuous connection of rebar can be achieved by welding or careful binding. If welding is not possible for statics reasons, auxiliary steel structures should be added instead, which must be welded to each other and bound to the reinforcement. Continuous connection of the reinforcing bars of a building is only possible during the construction of the building (even if the building is made of prefabricated parts). Therefore, in the design stage of building structure and foundation, it is necessary to consider the steel structure and reinforcement for equipotential connection.

DIN VDE 0845 Part 1 :1987-10. The scope of application is quoted as follows:

This standard applies to the protection of dangerous or interfering surges in telecommunications systems. These surges are caused by electromagnetic interference, lightning effects or electrostatic charges, and therefore take into account equipment and transmission lines that are part of the telecommunications system.

DIN VDE 0185 Part 1 applies to external lightning protection (interception and ejecting of lightning) and DIN VDE 0855 Part 1 and 2 applies to antenna systems.

4. Electromagnetic Compatibility Standard including electromagnetic pulse and lightning protection (VG95372)

VG 95372:1996-03 summarizes the VG EMC standard that covers electromagnetic pulse and lightning protection.

5. Standards for components and protective equipment

International (IEC) and regional (CENELEC) standardization of components in surge protection systems and surge protection equipment is now well advanced, and national (DIN VDE) standards and drafts including testing authorizations are available. In the following paragraphs, these standards are considered only where it is necessary to understand how these components and protectors work and their potential use.

5.1 Connector [E DIN EN 50164-1(VDE 0185 Part 201)]

E DIN EN 50164-1(VDE 0185 Part 201), "Lightning protection elements -- Part 1: Requirements for connections", as of May 1997, applies to lightning protection elements (terminals, connectors). The draft details the requirements and testing of lightning current conduction connection elements. This standard will eventually replace the DIN national standard DIN 48810/8.86.

The draft standard Edin50164-1 is now being revised by the European Committee for Standardization (CENELEC). In addition to condition/life considerations (simulating an increase in corrosion pressure under actual conditions), the standard includes the following lightning flow (10/350us) tests.

Corresponding to the classification of the connection elements as marked by the manufacturer, the connection elements are divided into categories H and L and tested accordingly:

H(High load) Test current 100kA(10/350us)

L(normal load) Test current 50kA(10/350us)

Lightning current tests are based on criteria such as having sufficiently low contact resistance, no appreciable damage, deformation or relaxation, and meeting the release torque requirements for screw connections.

5.2 Lightning current arrester and surge arrester

A lightning current arrester (tested with a surge current of the 10/350us waveform) is different from a surge arrester (tested with an 8/20us waveform).

5.2.1 Arresters for power supply systems (IEC 61643-1/E DIN VDE 0675 Part 6)

The draft German standard E DIN VDE, Part 6, "Surge arresters for use in AC power supply systems rated at 100V to 1000V" has been in force since 1989.

EDIN VDE 0675-6 A1(VDE 0675 Part 6 /A1) "Amendment A1 to draft DIN VDE 0675-6(VDE 0675 Part 6)" was published in March 1996, and in October of the same year, E DIN VDE 0675-6 A2(VDE 0675 Part 6 A/2) "Amendment A2 to the draft DIN VDE 0675-6(VDE 0675 Part 6)" is published. DIN IEC 37A/44/CDV(VDE 0675 Part 601) "Surge protectors for Low-voltage distribution systems - Part 1: Performance requirements and test methods (IEC 37A/44/CDV:1996)" was also introduced in October 1996. This draft became the IEC standard and came into force in February 1998, and is used as part of IEC 61643-1, Surge Protectors connected to low-voltage distribution systems - Part 1: Performance requirements and test methods. Responsible for international standardization of arrester.

The yellow print of E DIN VDE0675 Part 6 /A1 is based on DIN VDE0675 Part 6 / Draft 1989-11, with the classification and classification of arrester types largely retained. These arresters are classified into four required grades:

Grade A. Arresters installed on low voltage overhead lines and in places where people cannot touch them are tested with surge current of 8/20us waveform.

Grade B. A lightning arrester installed for the purpose of protecting equipotential connections and controlling direct lightning strikes. These arresters are tested with a 10/350us waveform of simulated lightning test current Iimp.

Grade C. A lightning arrester installed for the purpose of surge protection in a fixed installation, as in a distribution area. These arresters are tested with a rated discharge surge current isn of 8/20us waveform.

Grade D. A lightning arrester installed for surge protection in a fixed or mobile device, especially in front of an electrical outlet area or terminal. The arrester group was tested using a composite wave generator (apparent internal resistance of 2Ω) that produced a 1.2/50us open surge voltage and an 8/20us short surge current. The open circuit voltage Uoc of the composite wave generator used for testing is specified as a parameter of these arresters.

The tests/corrections in Part A1 first consider electrical requirements and test procedures. Electrical requirements and testing procedures relevant to the user are briefly explained below:

1) Lightning test current (Iimp) for B-level arrester. Lightning test current Iimp (10/350us) replaces the previous 8/80us waveform of lightning test current. Iimp is determined by the following parameters: the peak value (Ipeak), the amount of charge (Q), the specific energy (W/R), and the waveform (10/350us). For the waveform, the value 10 represents the head rise time of 10us, and 350us represents the time from tail to half peak of the thunder wave of 350us. The 10/350us waveform of the lightning test current Iimp is closest to the first return current of the natural lightning discharge and is used in lightning simulation worldwide.

2) Determination of the measured value of limiting voltage (protection level Up). The test procedure for determining the limit voltage measurement is divided according to the type and grade of arrester. The limit voltage measurement is the maximum value obtained from different tests. The (arrester) protection level for the insulation fit is the maximum value of the limit voltage measurement.

3) Preconditioning and operational load testing (discharge capacity). Based on this, the performance of the arrester is tested in terms of discharge capacity and quench ability. After the internal structure of arrester is known, a voltage source corresponding to its continuous current can be selected according to its required grade, and the pretreatment test can be conducted according to its required grade.

4) Trip device and thermal stability of arrester. When testing the trip device and thermal stability of arresters there is a difference between arresters with spark gap and arresters based on nonlinear resistance. This difference is intended to simulate close to the actual cause of the failure:

Arrester based on nonlinear resistance. It is assumed that after many years of operation, due to repeated exposure to surge current, the leakage current will increase, which will lead to heat or power consumption of the arrester. This "thermal drift" was simulated in the trip test. The trip device must detach the arrester from the system before the housing overheats, which can result in a fire hazard.

Arrester with spark gap or series spark gap. The assumed cause of the fault is that the discharge current is too frequent and too large, or the number of extinguishes the continuous current is too much, and the electrode with built-in spark gap is melted and short circuit occurs. In the test, a copper conductor short-circuited the spark gap to simulate this fault. The maximum backup fuse recognized by the manufacturer must remove the arrester from the system before it becomes appreciably damaged or poses a fire hazard. Selecting Important Data for a Lightning Arrester

Rated voltage Uc. The Uc value indicates the maximum rated operating voltage of the arrester, under which the arrester has qualified performance data.

The protection level is Up. This parameter represents the arrester's ability to limit interference to Up. The level of protection required for arresters depends on the installation location (overvoltage category) and/or the electrical insulation strength of the device being protected.

Discharge capacity. This parameter is crucial if the arrester must be selected according to the hazard presented (direct lightning strike, distant lightning strike, induced overvoltage).

This value represents the actual performance of the arrester and represents the lightning test current/surge current/compound surge that can be discharged safely without significantly affecting its function. This index is also reflected in the classification of arresters:

Lightning test current Iimp Level B

Surge current isn't or Imax Grade A, C

Composite wave Uoc grade D

Blocking ability/continuity extinguishing ability IF. This parameter is very important for spark gap arrester. This parameter indicates the limit at which the arrester automatically extinguishes the system current.

Trip device/spare fuse. This data is always important, especially if the arrester is overloaded or misused, or has aged from multiple discharges. Arresters designed in accordance with E DIN VDE 0675-6/A1 have been shown to be capable of switching to a safe failure state in the event of overload/trip devices and overload/failure during thermal stability tests. Match the lightning arrester to the required position

Class B arrester (lightning current arrester). Lightning current arresters are installed and applied in the power supply area of the building, where there may be a large portion of lightning current.

Class C arrester. The typical installation location of these surge arresters is in the distribution box. This is where the residual voltage of the lightning current arrester and the kA level surge current (8/20us) must be safely controlled.

Grade D arrester. These arresters are located either between the switchboard and the terminal or at an electrical outlet.

The requirement for a Class D arrester is considered in terms of the applied voltage of the Uoc, which is liable to cause danger, rather than the applied surge current, which should be limited to a low value. Typical dangerous voltage values in the range of 2.5~4kV (appear in the terminal input port, power socket). N-PE Arrester (E DIN VDE 0675 Part 6 /A2)

N-PE arresters in E DIN VDE 0675-6/A2(VDE 0675 Part 6/A2):1996-10 "Surge arresters - Part 6: Application in AC power supply systems rated from 100 to 1000V, Is standardized in Amendment A2 "to draft DIN VDE 0675-6(VDE 0675 Part 6). This arrester is installed between the neutral wire (N) and the protective wire (PE).

What is the task of this N-PE arrester? For personal protection reasons, class B and Class C arresters are usually installed in front of fault current circuit breakers (in the direction of energy flow). 3+1 circuit is used to ensure that the fault arrester can pass through the backup fuse of the TT system to safely trip. The three outer conductors L1, L2, and L3 are connected to the arrester and are connected to the neutral line N. Install the N-PE arrester between the neutral wire (N) and the protective wire (PE). In the event of a failure (short circuit) of the arrester (on the outer conductor), a short circuit current occurs between the considered outer conductor L and the neutral line N, which can be cut through the system standby fuse within a set time. If the arrester is installed between L and PE, the current flowing through the faulty arrester between L and PE in the TT system is insufficient to fuse the system's fuse. N-pe arresters must be able to pass the total interference current from L1, L2, and L3 to N.

5.2.2 Lightning Arresters for use in information technology (IEC SC 37A/E DIN VDE 0845 Part 2)

The draft German standard DIN VDE 0845 Part 2 "Data processing and telecommunications lightning discharges, electrostatic discharges and overvoltages from power stations" has been in effect since October 1993.

In this draft standard, there are differences between the following surge protection devices:

Clearance, including : surge arrester, gas discharge tube (or gas discharge tube), along the surface discharge arrester/air spark clearance; from the spark gap; (4) self-extinguishing gap.

Semiconductor protection elements and nonlinear resistors.

Surge limiter.

Protect and isolate transformers, including step-down transformers. DIN VDE 0845 Part 2 covers various components and surge protectors (surge limiter) as shown in this listing. In International (IEC) standards, components and protectors are treated separately in different draft standards:

A detailed description of the components (components of low voltage surge protection equipment) has just been given by the SC37B Committee. At this stage, there are four drafts:

Draft IEC 61647-1: Specification for Gas discharge tubes (GDT);

Draft IEC 61647-2: Avalanche Diode (ABD) specification;

Draft IEC 61647-3: Metal oxide Nonlinear Resistance (MOV) specification;

Draft IEC 61647-4: Specification for thyristor surge suppressors (TSS).

The specification for surge protection equipment is currently being developed by Committee SC 37A entitled:

IEC 61644-1: Surge protectors for connection to telecommunications and signal networks.

There are plans to complete the second part detailing the selection and application of surge protectors.

Since standardization is carried out by Committee SC 37A, it is possible to ensure the testing requirements of arresters for information technology and arresters for power supply technology, taking into account their level of requirements and the compatibility of application conditions.

The E DIN VDE 0845 Part 2 specification, printed in yellow, provides requirements and tests for surge protection equipment used in data processing and telecommunications technical installations.

The electrical requirements and testing of the surge limiter relevant to the user are briefly described below.

For surge limiter, the draft standard distinguishes between Class 1 and Class 2. Specifically, Class 1 surge limiter is used to prevent transient overvoltages (such as those caused by lightning), and Class 2 surge limiter is used in situations where additional AC disturbances lasting up to 0.5s must be considered. Selecting Important Data for a Lightning Arrester

Nominal voltage UN. The nominal voltage of a arrester is characteristic of the type and is usually equal to the nominal voltage of the system to which the arrester is applied.

Rated voltage UC. The UC value indicates the maximum rated operating voltage of the arrester under which the arrester reaches the given performance data. This value allows the user to select the arrester based on the maximum operating data required by the system or device.

Nominal current IN Nominal current is the maximum allowable operating current that can be carried by the current path of the arrester.

Operating frequency range. In the range of working frequency, the insertion loss of arrester is less than or equal to 3dB. Since arresters usually have low-pass characteristics, the operating frequency range is described by cut-off frequency fG.

For applications in digital transmission systems, a specific data transmission rate VS is used instead of the operating frequency range. The possible data transfer rate of the arrester depends on the transmission process used by the system. This process determines the necessary cutoff frequency in a system with low-pass characteristics. Eg. In telecommunications engineering, In practical engineering, VS=1.25fG

Carrying capacity/discharge capacity. The same standard applies here to arresters used in power supply systems.

DIN VDE 0845 Part 2 draft standard does not specify any requirements for lightning current arresters (lightning test current Iimp). In the present engineering practice, the lightning arrester used in information technology equipment can also conduct lightning current.

The protection level is UP.

This value is also referred to as "maximum residual pressure" in draft DIN VDE 0845 Part 2 standard. This parameter represents the highest voltage that may occur at the terminal of the arrester for a given load. When selecting a arrester, bear in mind that this value should be lower than the damage limit of subsequent equipment. Use lightning arresters based on requirements and positions

In the draft standard DIN VDE 0845 Part 2, the specific fit of the arrester for information technology equipment according to the requirements and location is not given. Only the load class is subdivided according to the load capacity of the arrester.

5.2.3 Lightning Arrester Coordination

Now that the requirements and levels of location of lightning currents and arresters are known, the user or project organizer must ensure that the arrester and protected equipment fit together. This is the only way to achieve optimal and coordinated protection of systems and equipment.