UNCA FSAE

Annotated Rules

EV.1 DEFINITIONS

EV.1.1 Tractive System – TS

Every part electrically connected to the Motor(s) and/or Accumulator(s)

EV.1.2 Grounded Low Voltage - GLV

Every electrical part that is not part of the Tractive System

EV.1.3 Accumulator

All the battery cells or super capacitors that store the electrical energy to be used by the Tractive System

EV.2 DOCUMENTATION

EV.2.1 Electrical System Form - ESF

EV.2.1.1 Each team must submit an Electrical System Form (ESF) with a clearly structured documentation of the entire vehicle electrical system (including control and Tractive System).

Submission and approval of the ESF does not mean that the vehicle will automatically pass Electrical Technical Inspection with the described items / parts.

EV.2.1.2 The ESF may provide guidance or more details than the Formula SAE Rules.

EV.2.1.3 Use the format provided and submit the ESF as given in section DR - Document Requirements

EV.2.2 Submission Penalties

Penalties for the ESF are imposed as given in section DR - Document Requirements.

EV.3 ELECTRICAL LIMITATIONS

EV.3.1 Operation

EV.3.1.1 Supplying power to the motor to drive the vehicle in reverse is prohibited

EV.3.1.2 Drive by wire control of wheel torque is permitted

EV.3.1.3 Any algorithm or electronic control unit that can adjust the requested wheel torque may only decrease the total driver requested torque and must not increase it

EV.3.2 Energy Meter

EV.3.2.1 All Electric Vehicles must run with the Energy Meter provided by the organizer

Refer to the FSAEOnline Website AD.2.2 for detail information on the Energy Meter

EV.3.2.2 The Energy Meter must be installed in an easily accessible location

EV.3.2.3 All Tractive System power must flow through the Energy Meter

EV.3.2.4 Power and Voltage limits will be checked by the Energy Meter data

Energy is calculated as the time integrated value of the measured voltage multiplied by the measured current logged by the Energy Meter.

EV.3.3 Power and Voltage

EV.3.3.1 The maximum power measured by the Energy Meter must not exceed 80 kW

EV.3.3.2 The maximum permitted voltage that may occur between any two points must not exceed 600 V DC

EV.3.3.3 The powertrain must not regenerate energy when vehicle speed is between 0 and 5 km/hr

EV.3.4 Violations

EV.3.4.1 A Violation occurs when one or two of these exist:

a. Use of more than the specified maximum power EV.3.3.1

b. Exceed the maximum voltage EV.3.3.2

for one or both conditions:

Continuously for 100 ms or more
After a moving average over 500 ms is applied

EV.3.4.2 Missing Energy Meter data due to the team’s fault, tampering, or attempting to tamper with the Energy Meter will be treated as a Violation.

EV.3.4.3 Tampering, or attempting to tamper with the Energy Meter or its data may result in Disqualification (DQ)

EV.3.5 Penalties

EV.3.5.1 Violations during the Acceleration, Skidpad, Autocross Events:

a. Each run with one or more Violations will Disqualify (DQ) the best run of the team

b. Multiple runs with Violations will DQ multiple runs, ex two runs with Violations DQ the two best runs

EV.3.5.2 Violations during the Endurance event:

Each Violation: 60 second penalty D.14.2.1

EV.3.5.3 Repeated Violations may void Inspection Approval or receive additional penalties up to and including Disqualification, subject to official discretion.

EV.3.5.4 The respective data of each run in which a team has a Violation and the resulting decision may be made public.

EV.4 COMPONENTS

EV.4.1 Motors

EV.4.1.1 Only electrical motors are allowed. The number of motors is not limited.

EV.4.1.2 Motors must meet T.5.3

EV.4.1.3 If used, Outboard Wheel Motors, where the motor, attendant cables and wiring do not meet F.11.1.3, must:

a. Include an Interlock EV.7.8

This Interlock(s) must Open the Shutdown Circuit EV.7.2.2 before failure of the Tractive System wiring when the wiring is damaged or the Wheel/Motor assembly is damaged or knocked off the vehicle.

b. Reduce the length of the portions of wiring and other connections that do not meet F.11.1.3 to the extent possible

EV.4.2 Motor Controller

The Tractive System Motor(s) must be connected to the Accumulator through a Motor Controller. No direct connections between Motor(s) and Accumulator.

EV.4.3 Accumulator Container

EV.4.3.1 Accumulator Containers must meet F.10

EV.4.3.2 The Accumulator Container(s) must be removable from the vehicle while still remaining rules compliant

EV.4.3.3 The Accumulator Container(s) must be completely closed at all times (when mounted to the vehicle and when removed from the vehicle) without the need to install extra protective covers

EV.4.3.4 The Accumulator Container(s) may contain Holes or Openings

a. Only the wiring harness, ventilation, cooling and fasteners may pass through holes in the Accumulator Container(s)

b. Holes and Openings in the Accumulator Container must meet F.10.4

c. External holes must meet EV.6.1

EV.4.3.5 Any Accumulators that may vent an explosive gas must have a ventilation system or pressure relief valve to release the vented gas

EV.4.3.6 Completely sealed Accumulator Containers must have a pressure relief valve

EV.4.3.7 Pressure relief valves must not have line of sight to the driver, with the Firewall installed or removed

EV.4.3.8 Each Accumulator Container must be labelled with the:

a. School Name and Vehicle Number

b. Symbol specified in ISO 7010-W012 (triangle with black lightning bolt on yellow background) with triangle side length of 100 mm minimum

c. Text “Always Energized”

d. Text “High Voltage” if the voltage meets T.9.1.1

EV.4.4 Grounded Low Voltage System

EV.4.4.1 The GLV System must be:

a. A Low Voltage system that is Grounded to the Chassis

b. Able to operate with Accumulator removed from the vehicle

EV.4.4.2 The GLV System must include a Master Switch, see EV.7.9.1

EV.4.4.3 A GLV Measuring Point (GLVMP) must be installed which is:

a. Connected to GLV System Ground

b. Next to the TSMP EV.5.8

c. 4 mm shrouded banana jack

d. Color: Black

e. Marked “GND”

EV.4.4.4 Low Voltage Batteries must meet T.9.2

EV.4.5 Accelerator Pedal Position Sensor - APPS

Refer to T.4.2 for specific requirements of the APPS

EV.4.6 Brake System Encoder - BSE

Refer to T.4.3 for specific requirements of the BSE

EV.4.7 APPS / Brake Pedal Plausibility Check

EV.4.7.1 Must monitor for the two conditions:

The mechanical brakes are engaged EV.4.6, T.3.2.4
The APPS signals more than 25% Pedal Travel EV.4.5

EV.4.7.2 If the two conditions in EV.4.7.1 occur at the same time:

a. Power to the Motor(s) must be immediately and completely shut down

b. The Motor shut down must stay active until the APPS signals less than 5% Pedal Travel, with or without brake operation

The team must be able to demonstrate these actions at Technical Inspection

EV.4.8 Tractive System Part Positioning

All parts belonging to the Tractive System must meet F.10.5.8

EV.4.9 Housings and Enclosures

EV.4.9.1 Every housing or enclosure containing parts of the Tractive System other than Motor housings, must be labelled with the:

a. Symbol specified in ISO 7010-W012 (triangle with black lightning bolt on yellow

background)

b. Text “High Voltage” if the voltage meets T.9.1.1

EV.4.9.2 If the material of the housing containing parts of the Tractive System is electrically conductive, it must have a low resistance connection to GLV System Ground, see EV.6.7

EV.4.10 Accumulator Hand Cart

EV.4.10.1 Teams must have a Hand Cart to transport their Accumulator Container(s)

EV.4.10.2 The Hand Cart must be used when the Accumulator Container(s) are transported on the competition site EV.11.4.2 EV.11.5.1

EV.4.10.3 The Hand Cart must:

a. Be able to carry the load of the Accumulator Container(s) without tipping over

b. Contain a minimum of two wheels

c. Have a brake that must be:

Released only using a dead man type switch (where the brake is always on except when released by pushing and holding a handle) or by manually lifting part of the cart off the ground

Able to stop the Hand Cart with a fully loaded Accumulator Container

EV.4.10.4 Accumulator Container(s) must be securely attached to the Hand Cart

EV.5 ENERGY STORAGE

EV.5.1 Accumulator

EV.5.1.1 All cells or super capacitors which store the Tractive System energy are built into Accumulator Segments and must be enclosed in (an) Accumulator Container(s).

EV.5.1.2 Each Accumulator Segment must contain:

Maximum static voltage of less than 120 V DC

Maximum energy of 6 MJ

The contained energy of a stack is calculated by multiplying the maximum stack voltage with the nominal capacity of the used cell(s).

EV.5.1.3 No further energy storage except for reasonably sized intermediate circuit capacitors are allowed after the Energy Meter EV.3.1

EV.5.1.4 All Accumulator Segments and/or Accumulator Containers (including spares and replacement parts) must be identical to the design documented in the ESF and SES

EV.5.2 Electrical Configuration

EV.5.2.1 All Tractive System components must be rated for the maximum Tractive System voltage

EV.5.2.2 If the Accumulator Container is made from an electrically conductive material:

a. The poles of the Accumulator Segment(s) and/or cells must be isolated from the inner wall of the Accumulator Container with an insulating material that is rated for the maximum Tractive System voltage.

b. All conductive surfaces on the outside of the Accumulator Container must have a low resistance connection to the GLV System Ground, see EV.6.7

c. Any conductive penetrations, such as mounting hardware, must be protected against puncturing the insulating barrier.

EV.5.2.3 Each Accumulator Segment must be electrically insulated with suitable Nonflammable Material (F.1.18) (not air) for the two:

a. Between the segments in the container

b. On top of the segment

The intent is to prevent arc flashes caused by inter segment contact or by parts/tools accidentally falling into the container during maintenance for example.

EV.5.2.4 Soldering electrical connections in the high current path is prohibited

Soldering wires to cells for the voltage monitoring input of the AMS is allowed, these wires are not part of the high current path.

EV.5.2.5 Every wire used in an Accumulator Container, whether it is part of the GLV or Tractive System, must be rated to the maximum Tractive System voltage.

EV.5.3 Maintenance Plugs

EV.5.3.1 Maintenance Plugs must allow electrical separation of the Accumulator Segments to meet:

a. The separated Segments meet voltage and energy limits of EV.5.1.2

b. The separation must affect both poles of the Segment

EV.5.3.2 Maintenance Plugs must:

a. Require the physical removal or separation of a component. Contactors or switches are not acceptable Maintenance Plugs

b. Have access after opening the Accumulator Container and not necessary to move or remove any other components

c. Not be physically possible to connect in any configuration other than the design intended configuration

d. Not require tools to install or remove

e. Include a positive locking feature which prevents the plug from unintentionally becoming loose

f. Be nonconductive on surfaces that do not provide any electrical connection

EV.5.3.3 When the Accumulator Containers are opened or Segments are removed, the Accumulator Segments must be separated by using the Maintenance Plugs. See EV.11.4.1

EV.5.4 Accumulator Isolation Relays - AIR

EV.5.4.1 Every Accumulator Container must contain minimum one fuse (EV.6.6) and two or more Accumulator Isolation Relays (AIR)

EV.5.4.2 The Accumulator Isolation Relays must:

a. Be a Normally Open type

b. Open both poles of the Accumulator

EV.5.4.3 When the AIRs are open, High Voltage T.9.1.1 must not be external of the Accumulator Container

EV.5.4.4 The Accumulator Isolation Relays and any fuses must be separated from the rest of the Accumulator with an electrically insulated and Nonflammable Material (F.1.18).

EV.5.4.5 A capacitor may be used to hold the AIRs closed for up to 250 ms after the Shutdown Circuit Opens EV.7.2.2

EV.5.5 High Voltage Disconnect - HVD

A High Voltage Disconnect (HVD) must be included to quickly disconnect one or both poles of the Accumulator EV.11.3.2

EV.5.5.1 The High Voltage Disconnect (HVD) must be:

a. A directly accessible element, fuse or connector

b. More than 350 mm from the ground

c. Easily visible when standing behind the vehicle

d. Operable in 10 seconds or less by an untrained person

e. Operable without removing any bodywork or obstruction or using tools

f. Directly operated. Remote operation through a long handle, rope or wire is not acceptable.

g. Clearly marked with "HVD"

EV.5.5.2 An Interlock EV.7.8 must Open the Shutdown Circuit EV.7.2.2 when the HVD is removed

EV.5.5.3 A dummy connector or similar may be used to restore isolation to meet EV.6.1.2

EV.5.6 Precharge and Discharge Circuits

EV.5.6.1 The Accumulator must contain a Precharge Circuit. The Precharge Circuit must:

a. Be able to charge the Intermediate Circuit to minimum 90% of the Accumulator voltage

before closing the second AIR

b. Be supplied from the Shutdown Circuit EV.7.1

c. Not be fused

EV.5.6.2 The Intermediate Circuit must precharge before closing the second AIR. The end of precharge must be controlled by one of the following two options:

a. Feedback by monitoring the voltage in the Intermediate Circuit

b. A conservative time defined by the longer of:

Twice the time to charge to 90%
The time to charge to 90% plus 500ms

EV.5.6.3 The Tractive System must contain a Discharge Circuit. The Discharge Circuit must be:

a. Wired in a way that it is always active when the Shutdown Circuit is open

b. Able to discharge the Intermediate Circuit capacitors if the HVD has been opened

c. Not be fused

d. Designed to handle the maximum Tractive System voltage for minimum 15 seconds

EV.5.6.4 Positive Temperature Coefficient (PTC) devices must not be used to limit current for the Precharge Circuit or Discharge Circuit

EV.5.6.5 The precharge relay must be a mechanical type relay

EV.5.7 Voltage Indicator

Each Accumulator Container must have a prominent indicator when High Voltage T.9.1.1 is

present at the vehicle side of the AIRs

EV.5.7.1 The Voltage Indicator must always function, including when the Accumulator Container is disconnected or removed

EV.5.7.2 The voltage being present at the connectors must directly control the Voltage Indicator using hard wired electronics with no software control.

EV.5.7.3 The control signal which closes the AIRs must not control the Voltage Indicator

EV.5.7.4 The Voltage Indicator must:

a. Be located where it is clearly visible when connecting/disconnecting the Accumulator Tractive System connections

b. Be labeled “High Voltage Present”

EV.5.8 Tractive System Measuring Points - TSMP

EV.5.8.1 Two Tractive System Measuring Points (TSMP) must be installed in the vehicle which are:

a. Connected to the positive and negative motor controller/inverter supply lines

b. Next to the Master Switches EV.7.9

c. Protected by a nonconductive housing that can be opened without tools

d. Protected from being touched with bare hands / fingers once the housing is opened

EV.5.8.2 Two TSMPs must be installed in the Charger EV.8.2 which are:

a. Connected to the positive and negative Charger output lines

b. Available during charging of any Accumulator(s)

EV.5.8.3 The TSMPs must be:

a. 4 mm shrouded banana jacks rated to an appropriate voltage level

b. Color: Red

c. Marked “HV+” and “HV-”

EV.5.8.4 Each TSMP must be secured with a current limiting resistor.

a. The resistor must be sized per the following:

Maximum TS Voltage (Vmax) Resistor Value

Vmax <= 200 V DC 5 kOhm

200 V DC < Vmax <= 400 V DC 10 kOhm

400 V DC < Vmax <= 600 V DC 15 kOhm

b. Resistor continuous power rating must be more than the power dissipated across the TSMPs if they are shorted together

c. Direct measurement of the value of the resistor must be possible during Electrical Technical Inspection.

EV.5.8.5 Any TSMP must not contain additional Overcurrent Protection.

EV.5.9 Tractive System Active Light - TSAL

EV.5.9.1 The vehicle must include a Tractive Systems Active Light (TSAL) that must:

a. Illuminate when the GLV System is energized to indicate the status of the Tractive System

b. Be directly controlled by the voltage present in the Tractive System using hard wired electronics. Software control is not permitted.

c. Not perform any other functions.

EV.5.9.2 The TSAL may be composed of multiple lights inside a single housing

EV.5.9.3 When the voltage outside the Accumulator Container(s) exceeds T.9.1.1, the TSAL must:

a. Be Color: Red

b. Flash with a frequency between 2 Hz and 5 Hz

EV.5.9.4 When the voltage outside the Accumulator Container(s) is below T.9.1.1, the TSAL must:

a. Be Color: Green

b. Stay continuously illuminated

EV.5.9.5 The TSAL mounting location must:

a. Be near the Main Hoop at the highest point of the vehicle.

b. Be inside the Rollover Protection Envelope F.1.13

c. Be no lower than 150 mm from the highest point of the Main Hoop.

d. Not allow contact with the driver’s helmet in any circumstances.

e. Not be in proximity to other lights.

EV.5.9.6 The TSAL must be visible:

a. From every horizontal direction, except small angles which are blocked by the Main Hoop

b. From a point 1.6 m vertically from ground level, inside a 3 m horizontal radius from the TSAL

c. In direct sunlight

EV.5.10 Connectors

Tractive System connectors outside of a housing must meet one of the two:

- Contain an Interlock EV.7.8 which must Open the Shutdown Circuit EV.7.2.2
- Be sealed at Tech Inspection IN.4.7.1

EV.6 ELECTRICAL SYSTEM

EV.6.1 Covers

EV.6.1.1 Nonconductive material or covers must prevent inadvertent human contact with any Tractive System voltage.

Covers must be secure and sufficiently rigid.

Removable Bodywork is not suitable to enclose Tractive System connections.

EV.6.1.2 Contact with any Tractive System connections with a 100 mm long, 6 mm diameter insulated test probe must not be possible when the Tractive System enclosures are in place.

EV.6.1.3 Tractive System components and Accumulator Containers must be protected from moisture, rain or puddles.

A rating of IP65 is recommended

EV.6.2 Insulation

EV.6.2.1 Insulation material must:

a. Be appropriate for the expected surrounding temperatures

b. Have a minimum temperature rating of 90°C

EV.6.2.2 Insulating tape or paint may be part of the insulation, but must not be the only insulation.

EV.6.3 Wiring

EV.6.3.1 All wires and terminals and other conductors used in the Tractive System must be sized for the continuous current they will conduct

EV.6.3.2 All Tractive System wiring must:

a. Be marked with wire gauge, temperature rating and insulation voltage rating.

A serial number or a norm printed on the wire is sufficient if this serial number or norm is clearly bound to the wire characteristics for example by a data sheet.

b. Have temperature rating more than or equal to 90°C

EV.6.3.3 Tractive System wiring must be:

a. Done to professional standards with sufficient strain relief

b. Protected from loosening due to vibration

c. Protected against damage by rotating and / or moving parts

d. Located out of the way of possible snagging or damage

EV.6.3.4 Any Tractive System wiring that runs outside of electrical enclosures:

a. Must meet one of:

Enclosed in separate orange nonconductive conduit
Use an orange shielded cable.

b. Must meet one of:

Run in a fully enclosed container. Bodywork is not an enclosure.
The conduit or shielded cable is securely anchored at each end to allow it to withstand a force of 200 N without straining the cable end crimp

c. Any shielded cable must have the shield grounded.

EV.6.3.5 Wiring that is not part of the Tractive System must not use orange wiring or conduit.

EV.6.4 Connections

EV.6.4.1 All Tractive System connections must:

a. Be designed to use intentional current paths through conductors designed for electrical current

b. Not rely on steel bolts to be the primary conductor

c. Not include compressible material such as plastic in the stack-up

EV.6.4.2 If external, uninsulated heat sinks are used, they must be properly grounded to the GLV System Ground, see EV.6.7

EV.6.4.3 Bolted electrical connections in the high current path of the Tractive System must include a positive locking feature to prevent unintentional loosening

Lock washers or thread locking compounds (Loctite®) or adhesives are not acceptable.

Bolts with nylon patches are allowed for blind connections into OEM components.

EV.6.4.4 Information about the electrical connections supporting the high current path must be available at Electrical Technical Inspection

EV.6.5 Voltage Separation

EV.6.5.1 Separation of Tractive System and GLV System:

a. The entire Tractive System and GLV System must be completely galvanically separated.

b. The border between Tractive and GLV System is the galvanic isolation between both systems. Therefore, some components, such as the Motor Controller, may be part of both systems.

EV.6.5.2 There must be no connection between the Chassis of the vehicle (or any other conductive surface that might be inadvertently touched by a person), and any part of any Tractive System circuits.

EV.6.5.3 Tractive System and GLV circuits must not run through the same conduit or connector, except as allowed in EV.7.8.4

EV.6.5.4 GLV Systems other than the AIRs EV.5.4, parts of the Precharge and Discharge Circuits EV.5.6, HV DC/DC converters, the AMS EV.7.3, the IMD EV.7.6, parts of the TSAL EV.5.9.1 the Energy Meter EV.3.1 and cooling fans must not be inside the Accumulator Container.

EV.6.5.5 Where both Tractive System and GLV are included inside an enclosure, they must meet one of the two:

a. Be separated by insulating barriers (in addition to the insulation on the wire) made of moisture resistant, UL recognized or equivalent insulating materials rated for 90° C or higher (such as Nomex based electrical insulation)

b. Maintain the following spacing through air, or over a surface (similar to those defined in UL1741):

U < 100 V DC 10 mm

100 V DC < U < 200 V DC 20 mm

U > 200 V DC 30 mm

EV.6.5.6 Spacing must be clearly defined. Components and cables capable of movement must be positively restrained to maintain spacing.

EV.6.5.7 If Tractive System and GLV are on the same circuit board:

a. They must be on separate, clearly defined and clearly marked areas of the board

b. Required spacing related to the spacing between traces / board areas are as follows:

Voltage Over Surface Thru Air (cut in board) Under Conformal Coating

0-50 V DC 1.6 mm 1.6 mm 1 mm

50-150 V DC 6.4 mm 3.2 mm 2 mm

150-300 V DC 9.5 mm 6.4 mm 3 mm

300-600 V DC 12.7 mm 9.5 mm 4 mm

EV.6.5.8 Teams must be prepared to show spacing on team built equipment

For inaccessible circuitry, spare boards or appropriate photographs must be available for inspection.

EV.6.5.9 All connections to external devices such as laptops from a Tractive System component must include galvanic isolation.

EV.6.6 Overcurrent Protection

EV.6.6.1 All electrical systems (both Low Voltage and High Voltage) must have appropriate Overcurrent Protection/Fusing.

EV.6.6.2 Unless otherwise allowed in the Rules, all Overcurrent Protection devices must:

a. Be rated for the highest voltage in the systems they protect.

Overcurrent Protection devices used for DC must be rated for DC and must carry a DC rating equal to or more than the system voltage

b. Have a continuous current rating less than or equal to the continuous current rating of any electrical component that it protects

c. Have an interrupt current rating higher than the theoretical short circuit current of the system that it protects

EV.6.6.3 Each parallel element of multiple parallel battery cells, capacitors, strings of battery cells, strings of capacitors, or conductors must have individual Overcurrent Protection.

EV.6.6.4 Any conductors (wires, busbars, etc) conducting the entire pack current must meet one of:

a. Be appropriately sized for the total current that the individual Overcurrent Protection devices could transmit

b. Contain additional Overcurrent Protection to protect the conductors

EV.6.6.5 Battery packs with Low Voltage or non voltage rated fusible links for cell connections may be used when all three conditions are met:

An Overcurrent Protection device rated at less than or equal to one third the sum of the parallel fusible links and complying with EV.6.6.2.b above is connected in series.
The AMS can detect an open fusible link and will Open the Shutdown Circuit EV.7.2.2 if a fault is detected.
Fusible link current rating is specified in manufacturer’s data or suitable test data is provided.

EV.6.6.6 If conductor ampacity is reduced below the ampacity of the upstream Overcurrent Protection, the reduced conductor longer than 150 mm must have additional Overcurrent Protection.

This additional Overcurrent Protection must be:

a. 150 mm or less from the source end of the reduced conductor

b. On both positive and negative conductors in the Tractive System

c. On the positive conductor in the Grounded Low Voltage System

EV.6.6.7 Cells with internal Overcurrent Protection may be used without external Overcurrent Protection if suitably rated.

Most cell internal Overcurrent Protection devices are Low Voltage or non voltage rated and conditions of EV.6.6.5 above will apply.

EV.6.7 Grounding

EV.6.7.1 Grounding is required for:

a. Parts of the vehicle which are 100 mm or less from any Tractive System component

b. The Tractive System Firewall T.1.9

EV.6.7.2 Grounded parts of the vehicle must have a resistance to GLV System Ground less than the values specified below.

a. Electrically conductive parts 300 mOhms (measured with a current of 1 A)

Examples: parts made of steel, (anodized) aluminum, any other metal parts

b. Parts which may become electrically conductive 5 Ohm

Example: carbon fiber parts

Carbon fiber parts may need special measures such as using copper mesh or similar to keep the ground resistance below 5 Ohms.

EV.6.7.3 Electrical conductivity of any part may be tested by checking any point which is likely to be conductive.

Where no convenient conductive point is available, an area of coating may be removed.

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