PEC (Section 1-5)

• Current through the body determines electric shock intensity
• Dependent on circuit and body impedance
• Moisture of adult whrn dry=1Mohm wet=1.5kohm
• Any current drawn from in excess of 30mA can be drawn through 1.5k ohm shall be classified as hazardous
• Potential difference between 2 exposed structure should be < 45v rms or 135Vdc
• Potential difference between two points on the floor in the direction of maximum gradient shall be < 45 vrms or 135 dc

• Use of fuse in series with the circuit

• Used to divert undesired currents before they reach the equipments
• Installed some distance away from the equipment
• ground resistance is the resistance path of a ground connection
• Should not exceed 5.0 ohm for equipment locations, antenna towers, 25 ohm for telephone poles and customer premise

The Philippine Electronics Code

Session 4: General Strenth Requirements

4.1: General

4.2: Loading Zone

4.3: Safety Factors

4.4:Transverse Strength Requirements

4.5: Vertical Strength Requirements

4.6: Longitudinal Strength Requirements

4.7: Ultimate Strength of Materials

4.8: Detailed Strength Requirements

Wood:

Structural steel

• Tension and Bending: max allowable stress = 23.2Kg/mm^2 x safety factor
• Compression: 1/fs(YP(YP-8.3472 ) /200)(1/r)
• Shear: tensile strength=2/3(3.867Kg/cm^2)/Safety factor

*multiply by 1.4 if natural plane is on the diagonal of a square

*multiply by .55 if loading being considered is a long time loading

• Employs to attain a sufficiently reliable level of safety.

• To keep foreign potential out of the communication facility or plant or when it manifests itself in the communication facility.

• Diverted to ground as near the point of entry and at the shortest time possible.

4.8.1: Poles, Towers and other structure

4.8.2: Crossarms

4.8.3: Pins and Conductor fastenings

4.8.4: Conductors

4.8.6: Guys and Anchors

4.8.7: Messengers and Span wires

4.8.8: Hardware

2. Fuses and Current Interrupting

• Current interrupting may be accomplished by employing one or any combination of Fuse Links, Heat coils, Fuse Cable, and Automatic Circuit Breaker.

• Fuses are effective only when its time and current operating characteristics are matched to that of the circuit it is intended to protect.

• Automatic circuit breaker opens the circuit when currents exceeds.

• This method should consider the cost of the protection measures/s against the value of service continuity and cost of system damage.

4. Grounding and Bonding

• Keeps the voltage to ground of metallic enclosures and other structures.

• Protects against static electricity with its attendant shock and fire hazards.

• No cut-out switch or fuse shall be placed in the ground lead.

• The copper grounding should be insulated.

• Ground conductors should be run only in NON-METALIC conduit or not in conduit.

• Water pipe ground shall be an addition to the primary grounding electrode system.

3. Surge Arresters

• Normally open circuited devices and pass no significant current at normal operating potentials.

• Its striking voltage must be constant after several successive discharges.

• Its Arcing voltage must be as small as possible.

• It must be capable of carrying several tens of amperes for periods of the order of one second.

• The surge arrester should be “fail safe”, this shall be achieved through final short-circuiting of the electrodes.

1. Lightning Rod

• Area within which strokes are likely to be diverted to a structure varies with the structure’s effective height.

• Material for the Lightning rod shall be of galvanized iron/steel, copper weld or other corrosion-resistant material.

• No. 2 AWG grounding conductors shall be run in the shortest route directly to the master ground bus or direct to earth without intervening splice or connection free from sharp bends.

• Shall be mounted a top structures not less than 30cm.

• All structures except nearby taller buildings or structures, Passive reflectors and other similar fully metallic structures, and Metallic antenna towers or poles, are required to provide lightning rod.

3.3: Methods and Material

3.3.1: Electrical Protection

3.3.2: Materials

3.3.3: Measurements

3.3.4: Determining Good Electrode Location

3.3.5: Maintenance

1. B) Fall of Potential/Three Terminal Test

- Uses two references rods and it is critical and the instructions of the instrument manufacturer must be followed.

1. C) Voltmeter-ammeter Method and Triangulation Method

2. A) Different Types of Soils exhibit different resistivity.

2. B) Conduction of current is largely electrolytic so the amount of moisture and salt content of the soil radically affects its resistivity.

2.C) An increase in temperature will decrease resistivity

2.D) Earth resistivity is a very variable quantity.

2.E) The deeper ground electrode gives a more stable and lower value of resistance.

2. Earth Resistivity

- expressed in ohm-centimeter is the resistance of parallel faces of a one cubic centimeter of soil.

- Earth is supposed to be a poor conductor compared to copper, but because of the area of a path for current is made large enough, resistance can be quite low and the earth can be a good conductor.

1. Ground Resistance Text Method

- Simple and straight- forward and instruments are mostly direct reading.

1. A) Direct Method/ Two Terminal Tests

Important consideration with this test:

• Reference ground or water system must be extensive enough to have a negligible resistance.

• Water pipe must be metallic throughout without any insulating couplings or flanges.

• Earth electrode under test must be far enough away from the water-piped system to be outside its sphere of influence.

a.) Drive rods in various locations to such depths as may be required and measure the resistances while the rods are being driven.

b.) Measure the earth resistivity before driving ground rods then calculate the number and length of rods required.

How to improve Grounds?

A. Lengthen the ground-electrode in the earth

B. Use Multiple Rods

C. Treat the soil if lengthening the ground-electrode and using multiple Rods is not feasible.

1. Ground system requirements from year to year can change depending on following

Factor:

a.) A plant or facility can expand in size or change its operation and such changes create

different needs in the grounding system.

b.) As more non-metallic pipes and conduits are installed underground, the less and less

dependable as effective low-resistance ground connection.

c.) Water table is gradually falling, and grounds formerly effective may end up

ineffective.

2. Ground resistance shall be tested when installed.

3. All ground connections, be it solder less or soldered, shall be checked at least once

Each year to be sure they are tight.

Session 5: Indoor Plant Safety Rules

5.1: General rule- for all electronics and communications equipment installed and/or located inside buildings or in sheltered structures, except consumer products

5.1.1 no SHOCK, CASUALTY, or FIRE HAZARD shall result when used or operated

5.1.2-3 Grounding system

5.1.9-11 coordination of electrical protection measures and only those approved shall be used for protection of the users

5.1.12 location of fuel tanks

5.1.13-14 specifications for building ground ring conductor

5.1.4 rise on accessible parts

5.1.5 strength consideration for installation

5.1.6 no hazardous emission of fumes, chemicals, radiations, etc

5.1.7 users shall be protected from shock or

fire hazards (look for video)

5.1.8 user’s responsibility

5.1.15 markings for further instructions on points with hazardous voltage

5.1.16 when working with hazardous voltage, the following shall be observed

5.1.17 circuitry for draining or removal of excess charge

5.1.18 stationary battery installation mounted on racks shall be fitted with earthquake bracings

5.2:radio transmitting and receiving safety requirements

D. AC power requirement for certain equipment

E. Made electrodes

5.2.2 mobile station:

1. Land mobile

2. Maritime Mobile

3. Aeromobile

5.2.1 Fixed Station

A. not to be struck directly by lightning

B. involves special consideration

C. Based on preventing voltage surges from reaching a component or equipment

A. Safety provisions for counterpart base station

B. No increase of injury for the driver or pilot and passengers in terms of installation of devices

C. Battery cables shall be fused

D. Current carrying capacity of less than 250% of the peak load current for battery cables

E. Insulation strength rating of not less than 10 times the maximum voltage for battery cables

F. Current overloads due to equipment or wiring malfunction shall not affect other vital navigation equipment

G. electronic and communication installations in larger water craft

H. Approved for marine application cables are to be used

5.3 Switching Equipment safety requirements – (telephone, telegraph, telex)

5.3.1 switching equipment is subject to damage from lightning and power fault currents

5.3.2 surge arresters and rating shall be connected on all wire circuits entering the building except:

1. entire length in underground

2. not bunched with a circuit any portion of which is installed above ground level

3. not bridged to any wire circuit that may be exposed to potential contact

5.3.5 earth electrodes shall be bonded to:

1. continuous buried metallic public water pipe system

2. continuous buried metallic private water system

3. deep well metal casing

5.3.6 connections using methods and clamps in this CODE

5.3.7 ground bar shall be used for big offices

5.1: General Rules

5.2: Radio Transmitting & Receiving Installation Safety Requirement

5.3: Switching Equipment Installation Safety Requirement

5.4: Computer And Data Installation Safety Requrements

5.5: Station Installation Safety Requirement

5.3.8 ground conductor sizes

5.3.9 PVC for insulation of cables

5.3.10 non-combustible office furniture

5.3.11 maintenance supply storage external to the switching rooms

5.3.3 arresters should be fitted on power services serving the station

5.3.4 switching office earth electrode should be any made electrodes

5.4 computer and data safety requirements

5.4.1 EDP equipment is AC operated

5.4.2 the computer is the vital nerve center in any EDP installation

5.4.3 the computer require special environment conditions

Session 3: General Electrical Protection and Grounding Requirements

5.5 station safety requirements

Measures Covered:

3.1: General

• Effects of lightning
• Accidental contact with power lines
• Voltage induced communication by normal or fault currents in parallel runs of power supply
• Rising of local earth potential due to lightning or power fault currents

3.2 Protection Methods

5.5.5 Customer equipment safety requirements

5.5.6 PBX/PABX

5.5.7 Telephone instruments

5.5.8 Data and Telegraph Terminals

5.5.1 protectors-Electrical protection, station installations, etc

5.5.2 Grounding and Bonding

5.5.3 Location

5.5.4 Special Occupancy

A. The primary considerations of electrical protection are:

B. The amount of protection to be adopted an employed is determined by a proper balance between:

Provision of grounded material such that foreign potential will be intercepted and surge currents diverted to the ground with least damage

C. Protection measures may be costly to add-up so it is desirable to consider them in the initial step

D. When human safeguarding of involved, communication entities should update its practice voluntarily and as soon as possible even if not required by the Code.

3.1.1: Objectives

• Cost of protection measures and amount required to maintain protection level
• Value of damage to loss of life and property and or service interruptions caused by electrical hazards

• Minimize electrical hazards to people
• Reduce damage to equipments and plant
• Eliminate any fire hazards
• Minimize acoustic shock

3.2.1: Shielding

• Prevents development of hazardous potential difference in communication plant by direct bonding or by use of surge arresters, disharge gaps, etc.

3.2.2:Voltage Limiting

3.1.2: Lightning

• Electrical discharge occuring from clouds to earth
• Surges can appear in various paths of communication systems and produce explosive effects, dielectric failure, and fusing of conductors
• The path it takes depends upon the impedance presented to its wavefront
• Behaves like radio frequencies
• Surges can reach indoor equipments

• Good construciton and adequate spacing between communication systems
• Provide path to ground on facilities
• Insulation on communication systems
• Equipments prone to power line contact shall be provided with protections
• Adequate protections on contact circuits
• Ground potential rise = ZxI
• Insulation of transformers

3.1.3: Power Conduction/Induction

3.2.3:Current Limiting and Interrupting

3.1.4: Acoustic Shock

• Results from abnormally high sound level
• Voltage surge by foreign potential (ex. lightning)
• Connect across the telephone receiver devices with two rectifiers in parallel with opposite polarities to reduce this effect
• The device should:

- Occupy a small space

- Not show changes in temperature and humidity

- Not degrade circuit performance

- Should operate such that the amplitude of sound pressure <120db above 2x10^4 microbar at 1kHz

Section 1: General Rules

3.2.4:Grounding and Bonding

3.1.5: Electric Shock

Made Ground:

-Electrode bound in the ground to establish low resistance electrical contact with the earth

1.1: Purpose of the Rules

• Establishment of standards

• Protection for Electronics and Communications components

1.2: Applicability of rules

• The requirements of the code do not apply to a plant constructed or redone before the establishment of the code.

1.3: Scope of the rules

• The rules are only for the assurance or safety an protection- not as complete construction specifications.

1.2.1 CONSTRUCTION AND RECONSTRUCTION

• Applies to constructed and reconstructed when the code is applied.

• Make sure construction and reconstruction would meet the requirements of the code

• Reconstruction is when the identity of the plant is changed EXCEPT FOR:

o Service Drops

o Suborinate element- when a new element is installed, it is required to follow all provisions in the PEC. It is not required for the current elements except when the new element is related to it.

o Replacements- when any supporting elements are replaced, it is considered reconstruction.

1.2.2. MAINTENANCE OF A PLANT

• There is a standard safety level in which a plant should be maintained

• Clearances and protection levels before issuance of the code is not reconstruction

• Changing clearance or protection for other purposes is reconstruction.

1.2.3. CONSTRUCTION PRIOR TO THE CODE

• The requirements of the code do not apply to a plant constructed or redone before the establishment of the code.

1.2.4. RECONSTRUCTION AND ALTERATION

• The PEC commission can mandate the reconstruction of a plant when the provisions stated in the code is not met.

1.5: Limiting Conditions Specified

• The clearances, strength, and protections found on the code are limiting expressions expressed in minimum or maximum values.

• The more rigorous condition in a requirement shall be applied when there are two or more requirements requiring limiting conditions.

• The greater the safety precaution (strength of construction, ample clearances, etc.) , the better

1.4: Equivalents

• Wire sizes specified in the code may be substituted with its nearest metric equivalent.

• The material of the wire can be substituted

• Flat or braided copper can be substituted with round or stranded copper as long as the current-carrying capacity is not less than the latter.

1.1: Purpose of the rules

1.2: Applicability of rules

1.3: Scope of the rules

1.4: Equivalents

1.5: Limiting Conditions Specified

1.6: Exemptions or Modifications

1.7: Saving Clause

1.6: Exemptions or Modifications

• The PEC allows exemption or modification of the requirements provided that it is accompanied by a justifiable reason for exemption or modification of the rule.

• The exemption or modification is only applicable to the particular case covered by the application.

1.7: Saving Clause

• The Commission can modify the provisions of the Code in situations where the public can be served better if it is done.

• The obedience of the code does not give a utility firm, entity, or group the permission not to conform to any legal requirement.

Session 2: Definition of Terms

• GROUND RING- a set of grounding conductors buried along the perimeter of a structure and is connected to an earth ground at one or more points.

• BUS- links two circuits together using a common location

• GUY- A tension member used to withstand an unbalanced force on a pole or other overhead line structure.

• ARRESTER GAS-FILLED- For over - voltage protection of telecommunication installations

• ARRESTER- device which reroutes high voltage away from the equipment and into ground

• GROUND- conducting connection where the circuit or equipment is connected to the earth

• GROUND BUS- where the grounds from individual pieces of equipment are connected and is connected to ground at one or more points.

• ACOUSTICS- science of sound

• ACOUSTIC SHOCK- experience of physical pain due to hearing very loud sound.

• AIR GAP- space between two magnetic materials or conductors

• ALIVE -another word for live;

- to have an electrical potential or charge different from that of the earth

• ALPETH- short for Aluminum Polyethylene

• DROPWIRE- used to run a user’s line from the main line or a pole of the provider to the user’s house or building.

• FLASHOVER- discharge through air produced by the application of voltage

• EXPOSED PART- a part which can be accidentally touched or approached nearer than a safe distance

GAS TUBE PROTECTOR:

• PROTECTOR- a device which gives protection from over voltage or over current

CARBON BLOCK PROTECTOR:

• GUARDED- protected in some way- barrier rails, casings, screens or covers to avoid dangerous contacts of any point of danger.

• HANDHOLE-underground opening where workers reach but not enter. It has a cover flush with the ground

• SAG-the maximum departure of a wire or cable in a given span from a straight line between the two points of support of the span at 60 degrees and no wind loading

LIGHNING ROD- a metallic rod that is placed on the highest point of a pole or a building and connected to earth that carries lightning currents directly to earth

• TENSION- Mechanical stress that stretches which tends to stretch or sever a material.

- Maximum allowable tension: ½ of tensile strength for guys and ¼ tensile strength for cables and wires

- Maximum working tension: the tension that is caused under the construction arrangement with the maximum loading conditions specified in Section 4.

• TOWER DISPLACEMENT, TOWER SWAY, TOWER TWIST