try lightning and function
https://developer.salesforce.com/docs/atlas.en-us.lightning.meta/lightning/expr_functions.htm
<aura:if isTrue="{!and(v.wrp.ObjectApiNAme!='Pay_Element_Master__c',
v.wrp.ObjectApiNAme!='CTC_Master__c',
v.wrp.ObjectApiNAme!='Section_Master__c')}">
<lightning:select name="select" label=" " aura:id="o" >
<option value="">None</option>
</lightning:select>
</aura:if>
Above code is not working now.
Updated code - 20-02-2018
<aura:if isTrue="{!and(
and(v.wrp.ObjectApiNAme!='Pay_Element_Master__c', v.wrp.ObjectApiNAme!='CTC_Master__c'),
v.wrp.ObjectApiNAme!='Section_Master__c')
)}">
<lightning:select name="select" label=" " aura:id="o" >
<option value="">None</option>
</lightning:select>
</aura:if>
You can wrap one and
condition inside another since lightning and
function work with only 2 parameters. below is the example
{!and( and(condition 11, condition 12), condition 2)}
{!and( and( and(condition 111, condition 112), condition 12), condition 2)}
Note: Since it is javascript, don't user capital AND. Use only small and