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Electro Mobility: Reliably securing charging infrastructure

Protecting equipment against the effects of lightning strikes as well as against power fluctuations on the network side is necessary. A direct hit by a lightning strike is devastating and hard to protect against, but the real danger for electronic devices of all kinds comes from the resultant electrical surge. In addition, all grid-side electrical switching operations that are connected to the grid, are potential sources of danger for the electronics in electric cars and charging stations. Short-circuits and earth faults can also be counted among the possible sources of damage to this equipment.

In order to be prepared against these electrical risks, it is absolutely necessary to take appropriate protective measures. Safeguarding expensive investments is imperative, and corresponding electrical standards prescribe the appropriate ways and means of safeguarding. There is a lot to consider, because the different sources of danger cannot be addressed with one solution for everything. This paper serves as an aid to identifying risk scenarios and the associated protection solutions, both on the AC and DC side.

Evaluate scenarios correctlyOvervoltages caused, for example, by direct or indirect lightning strikes into the alternating current (AC) network must be diminished up to the input of the main distributor of the EV charging device. It is therefore recommended to install Surge Protection Devices (SPDs) which conduct the impinging surge current to earth, directly after the main circuit breaker. A very good basis is provided by the comprehensive lightning protection standard IEC 62305-1 to 4 with its application examples. There, the risk assessment as well as external and internal lightning protection are discussed.

The lightning protection levels (LPL), which describe various mission critical applications, are decisive in this case. For example, LPL I includes the aircraft towers, which must still be operational even after a direct lightning strike (S1). LPL I also considers hospitals; where equipment must also be fully functional during thunderstorms and protected from fire hazard so that people are always as safe as possible.

With the increasing proliferation of electric vehicles, and the new “fast charging” technology, the need for a reliable and safe charging infrastructure is also increasing. Both the actual charging devices and the connected vehicles themselves need to be protected against overvoltages, as both have sensitive electronic components.

In order to evaluate the corresponding scenarios, it is necessary to assess the risk of a lightning strike and its effects. For this purpose, various characteristics are available, ranging from direct impact (S1) to indirect coupling (S4). In combination with the respective impact scenario (S1-S4) and the identified application type (LPL I-/ IV), the corresponding products for lightning and surge protection can be determined.

S3 Strike to incoming services(s)

S4 Strike near the incoming services(s)

3

4

S2

S1

3

4

S4

S3Incoming service

3

4

S2

S1

3

4

S4

S3Incoming service

Figure 1: Various lightning strike scenarios according to IEC 62305.

S1 Strike to the structure

S2 Strike near the structure

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The lightning protection levels for internal lightning protection are divided into four categories: LPL I is the highest level and is expected at 100 kA for the maximum load of a pulse inside an application. This means 200 kA for a lightning strike outside the respective application. Of this, 50 percent is discharged into the ground, and the "remaining" 100 kA is coupled into the interior of the building. In the case of a direct lightning strike risk S1, and an application of lightning protection level I (LPL I), the corresponding network must therefore be considered. The overview to the right provides the required value per conductor:

LPL Flash to StructureDirect and Indirect Flashes

to the Service

S1 (10/350) S1(8/20) S2 (8/20) S3 (10/350) S4 (8/20)

1 phase 3 phaseInductive Coupling

Induced Current

1 phase 3 phaseInductive Coupling

I 50 kA 25 kA 10 kA 0.2 kA 20 kA 10 kA 5 kA

II 35 kA 17.5 kA 7.5 kA 0.15 kA 15 kA 7.5 kA 3.75 kA

III / IV 25 kA 12.5 kA 5 kA 0.1 kA 10 kA 5 kA 2.5 kA

LPL IimpRule of Thumb

for LinkageInductive Coupling

I 200 kA 100 kA 5 kA

II 150 kA 75 kA 3.75 kA

III/IV 100 kA 50 kA 2.5 kA

Table 1: Various lightning strike scenarios according to IEC 62305.

The correct surge protection for the electrical charging infrastructure

Similar considerations need to be applied to electrical charging infrastructure. In addition to the AC side, the DC side must also be considered for some charging column technologies. It is therefore necessary to adopt the scenarios and values presented for the charging infrastructure of electric

EV ChargerTransformerStation

S1

S2

S3

S4

Charging station with various lightning strike scenarios according to IEC 62305.

vehicles. This simplified schematic illustration shows the structure of a charging station. A lightning protection level LPL III/IV is required. The below picture illustrates the scenarios S1 to S4:

These scenarios can give rise to the most varied forms of coupling.

EV ChargerTransformerStation

Charging station with various coupling options

These situations must be countered with lightning and surge protection. The following recommendations are available in this regard:

• For charging infrastructure without external lightning protection (induction current or mutual induction; values per conductor): only indirect coupling occurs here and only overvoltage protection precautions need to be taken. This is also shown in Table 2 on the pulse shape 8/20 µs, which stands for the overvoltage pulse.

LPL Flash to StructureDirect and Indirect

Flashes to the Service

S1 (8/20) S1 (8/20) S4 (8/20)

Inductive Coupling Induced Current Inductive Coupling

III/IV 5 kA 0.1 kA 2.5 kA

Values are per conductor

Values are per conductor

Table 2

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EV ChargerT2

MDB

AC

DCT2 T2 T2 T2 EV Charger

Charging station without LPS (lightning protection)

EV ChargerT1

MDB

AC

DCT2 T2 T2 T2 EV Charger

Charging station without LPS (lightning protection)

LPL Flash to StructureDirect and Indirect

Flashes to the Service

S1 (8/20) S1 (8/20) S3 (10/350) S4 (8/20)

Inductive Coupling Induced Current 1 phase 3 phase Inductive

Coupling

III/IV 5 kA 0.1 kA 10 kA 5 kA 2.5 kA

Table 3

• In this case showing direct and indirect coupling through an overhead line connection, the charging infrastructure has no external lightning protection. Here an increased lightning risk is discernible through the overhead line. It is therefore necessary to install lightning protection on the AC side. A three-phase connection requires at least 5 kA (10/350 µs) protection per conductor, see Table 3.

• For charging infrastructure with external lightning protection: The illustration on page 4 shows the designation LPZ, which stands for the so-called Lightning Protection Zone - i.e. the lightning protection zone that results in a definition of protection quality. LPZ0 is the outer area without protection; LPZ0B means that this area is "in the shadow" of the outer lightning protection. LPZ1 refers to the building entrance, for example the entry point on the AC side. The LPZ2 would represent a further sub-distribution inside the building.

In our scenario we can assume that products of LPZ0 / LPZ1 lightning protection products are required which are accord-ingly designated as T1 products (Type 1) (Class I per IEC or coarse protection). In the transition from LPZ1 to LPZ2 there is also talk of overvoltage protection T2 (Type 2), Class II per IEC or medium protection.

In our example in Table 4, this corresponds to an arrester with 4 x 12.5 kA for the AC connection, i.e. a total lightning current carrying capacity of 50 kA (10/350 µs). For AC/DC converters, appropriate overvoltage products must be selected. Attention: On the AC and DC side this must be done accordingly.

Values are per conductor

Meaning of external lightning protectionFor the charging stations themselves, the choice of the correct solution depends on whether the station is within the protection zone of the external lightning protection system. If this is the case, a T2 arrester is enough. In outdoor areas, a T1 arrester must be used according to the risk. See Table 4.

LPL Flash to Structure

S1 (8/20) S1 (8/20) S2 (8/20)

1 phase 3 phase Inductive Coupling Induced Current

III/IV 25 kA 12.5 kA 5 kA 0.1 kA

Values per conductor

Table 4

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EV ChargerT1

MDB

AC

DCT2 T2 T2 T1 EV Charger

LPZ 1

LPZ 0A

LPZ 0BLPZ 2

Charging station with LPS (lightning protection)

The right type and SPD to chooseThe smallest clamping voltage should be applied to the application to be protected. It is therefore important to select the correct design and the suitable SPD.

Compared to conventional arrester technology, Raycap's hybrid technology ensures the lowest overvoltage load on the equipment to be protected. With optimum overvoltage protection, the equipment to be protected has a negligible current flow of a safe size and low energy content (I2t) - the upstream residual current switch is not tripped.

Table 5: Overview of different surge protection types.

Important: Other sources of interference can also lead to overvoltage damage and therefore require appropriate protection. These can be switching operations on electrical systems that emit overvoltages, for example, or those that occur through lines inserted into the building (telephone, bus data lines).

A helpful rule of thumb: All metallic cable lines, such as gas, water or electricity, that lead into or out of a building are potential transmission elements for surge voltages. Therefore, in a risk assessment, the building should be examined for such possibilities and appropriate lightning / surge protection should be considered as close as possible to the sources of interference or building entry points.

Table 5 below provides an overview of the different types of surge protection available:

Type Designation SPD-TypesTest

CategoryReference Parameter

Lightning Arrester Type 1 Class I Iimp (Lightning Pulse Current 10/350µs)

Surge Protection Type 2 Class II In (Rated Current 8/20µs)

Terminal Protection Type 3 Class III Uoc (Open-Circuit Voltage)

Hybrid Technology

ConventionalTechnologyVo

ltage

TimeFigure 2: Compared to conventional arrester technology, Raycap's hybrid technology ensures the lowest overvoltage stress on the equipment to be protected.

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Back to the specific application of charging stations for electric cars: If charging devices are more than ten meters away from the main distribution board in which the primary surge protection is located, an additional SPD must be installed directly at the terminals of the AC side of the station in accordance with IEC 61643-12.

SPDs at the input of the main distribution board must be able to derive partial lightning currents (12.5 kA per phase), categorized as Class I according to IEC 61643-11, in accordance with Table 1, in the AC network without mains frequency in the event of lightning strikes. In addition, they must be free of leakage current (in pre-metering applications) and insensitive to short-term voltage peaks that can occur due to faults in the low-voltage network. This is the only way to guarantee a long service life and high SPD reliability. UL certification, ideally type 1CA or 2CA according to UL 1449, ensures worldwide applicability.

Raycap's hybrid technology is ideally suited for AC protection at the input of the main distribution board according to these requirements. Due to the leakage-free design, these devices can also be installed in the pre-meter area.

Special feature: Direct current applicationsElectric mobility also makes use of technologies such as rapid charging and battery storage systems. DC applications are specifically used here. This requires dedicated arresters with correspondingly extended safety requirements, such as larger air and creepage distances. Since the DC voltage, in contrast to the AC voltage, does not have a zero crossing, the resulting arcs cannot be automatically extinguished. As a result, fires can easily occur which is why an appropriate surge protection device must be used.

Since these components react very sensitively to overvoltages (low interference immunity), they must also be protected with appropriate protective devices. Otherwise they can be pre-damaged, which significantly shortens the service life of the components.

With its product ProBloc B 1000 DC, Raycap offers a solution designed for use in the DC range. Its main features include a compact design and a special high-performance disconnecting device that can be used to safely extinguish a switching arc. Due to the high self-extinguishing capacity, a prospective short-circuit current of 30 kA can be separated, as can be caused, for example, by battery storage.

Because the ProBloc B 1000 DC is a Type 1 and Type 2 arrester, it can be used universally for e-mobility applications on the DC side as lightning or surge protection. The nominal discharge current of this product is 20 kA per conductor. To ensure that insulation monitoring is not disturbed, it is recommended to use a leakage current-free arrester - this is also guaranteed with ProBloc B 1000 DC.

Another important aspect is the protective function in the event of overvoltages (UC). Here ProBloc B 1000 DC offers safety up to 1000 volts DC. As the protection level is <2.3 kV, the protection of the electric vehicle is ensured at the same time. A rated impulse voltage of 2.5 kV must be guaranteed for these cars. Thus if the wiring is correct the SPD also protects the electric car being charged. (Figure 3)

ProBloc B 1000 DC offers a corresponding color display that provides convenient status information about the viability of the product. With an integrated telecommunications contact, evaluations can also be carried out from remote locations.

Universal protection schemeThe Raycap standard solution with hybrid technology offers very good overvoltage protection for the scenarios shown and significantly reduces the risk of failures due to overvoltages. However, Raycap also offers its patented Strikesorb technology for high-risk areas and mission-critical charge parks. This technology is even safer due in large part to an oversized MOV encapsulated under 1500 pounds of pressure inside a robust aluminum housing. Strikesorb is the only surge protection solution designed to last for over 25 years, and is maintenance-free. The mostly fuse-free integration can withstand several thousand short duration strikes (such as those caused by lightning) and is globally certified to safety standards. If correctly installed, Strikesorb cannot explode or catch fire, has a controlled life-end mode, can carry extremely high short-circuit currents and has the best protection level of all the Raycap SPD products. This protection is recommended for complex and large installations powered by a central converter. (Figure 3)

ProBloc B 1000DC

-/++/-

Strikesorb 35-P-HV-M

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Raycap offers the most comprehensive product portfolio on the market, with a device for any scenario and many times more than just one. For all of the above cases Raycap products can reliably secure the entire charging infrastructure - both universal IEC solutions and UL-certified products.

SummarySpecial scenarios cannot be covered comprehensively with universal solutions - just as a Swiss Army Knife can not replace a well-equipped tool set. This also applies to the environment of EV charging stations and electric cars, especially since appropriate measuring, control and regulation instruments should ideally also be included in the protection

EV Charger

AC

DC

Charging Station

SPD SPD SPD

ProTec T1H ProTec T1 ProTec T2 RayDin

ProBloc B 1000 DCRayDat Strikesorb 35-P-HV-M

*If I, >10m another set ofSPDs is needed.

SafeTec T2-1000DC-3+0(-R)

Strikesorb 40ProTec ZPS

solution. It is important both to have the right equipment and to make the right choice depending upon the situation. If you take this into consideration, you will find a high-reliability business segment in electro mobility - and a suitable partner in Raycap.

Figure 3: Possible options of lightning and surge protection devices.

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About RaycapRaycap is a technology leader in lightning and surge protection solutions. The company has grown steadily since its inception in 1987. With more than 1,200 employees worldwide, its own accredited and certified test laboratories and numerous patents, Raycap product quality, reliability and innovation are guaranteed. All surge protection products are tested and certified independently to international standards (Type 1 to 3) according to UL, IEC and EN.

Customers come from a wide range of industries, including building/construction, telecommunications, energy (photovoltaic, wind, power generation in general and energy storage), e-mobility and rail.

More information is available at www.raycap.de and www.raycap.com.

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© 2019 Raycap All Rights Reserved.G09-00-124 190612

Raycap GmbHParkring 11

85478 Garching Munich

info@raycap.com

Contact Raycap if you need technical assistance about how to protect against surge or overvoltage damage, or if you have questions about your applications.

Sources:IEC 62305 Part 1 to 4, DIN VDE 0100-534, DIN VDE 0100-443IEC 61643-41, IEC 61643-11, IEC 61643-12